The ObserverIP will not pick up the Acurite 5-in-1. The only reason the Ambient picks up some Ecowitt sensors is because they are all Fine Offset clones.
If you get the WS-2902-ARRAY it will obviously work with any Ambient console that is; WS-2000, WS-2902A and ObserverIP. The combination of WS-2902-ARRAY + ObserverIP is actually called a WS-1550-IP.
If you have any of the previous stations I mentioned with the WS-2902-ARRAY then you can also pick up that outdoor sensor array with the Ecowitt GW1000.
If you go with the Ecowitt outdoor array (the all in one) like the HP2551 or HP3500B then the GW1000 will also pick them up. I'm not sure if the ObserverIP will pick them up. But you can get an ObserverIP that is branded by Ecowitt and then it should work.
If you get the separate components like the Ecowitt HP3501 then again I don't know if the ObserverIP will pick them up. Again you may need the Ecowitt version of the ObserverIP. But the GW1000 will pick up these separate components.
Notice that when I say ObserverIP I'm referring to the Ambient branded version, unless I specify otherwise.
Like I said I don't have all of these configurations and my knowledge regarding all possible combinations is limited...But this much I've said I'm confident in.
You asked which one I would get. Well I started with a WS-2902A before the WS-2000 was available. Then I upgraded the console to get a WS-2000. Then I added a GW1000 and it picks up the WS-2902-ARRAY just fine. My GW1000 picks up my Ecowitt PM2.5 but the WS-2000 does not see the PM2.5. Now I do know that Ambient will soon release their version of the PM2.5 and then the WS-2000 will pick it up. I don't have a soil sensor but I believe the same applies.
My requirements before I got anything was to get something that would work with the Meteobridge. That is why I then added an ObserverIP. I basically now have 4 consoles running at the same time; WS-2902A, WS-2000, ObserverIP, and GW1000. They all at the same time are picking up the single WS-2902-ARRAY that I have. The ObserverIP feeds the Meteobridge. I actually have 5 consoles because I have a second ObserverIP to mess with as I test WeeWx with ObserverIP driver and with Interceptor driver. I also have extra Ambient indoor temp/humidity sensor WH31 and that is picked up by the following: WS-2000, ObserverIP and the GW1000.
Continuing on to which I would get today. Definitely the WS-2000. That display is just awesome. If you want the Meteobridge to work then you just add the ObserverIP to the mix. Or you can probably get a better deal to get the WS-1550-IP and then add just the WS-2000 display console. If you want to have more fun then also add the Ecowitt GW1000...or wait on that till further work is done to integrate it as a replacement for the ObserverIP.
The Ecowitt separate components are very intriguing because you end up with separate components and a larger rain gauge that might be more accurate (not that the WS-2902-ARRAY rain gauge seem in appropriate that I can tell....but you know they say you lose some in heavier rains...I haven't looked into this yet). So the Ecowitt separates seem interesting for wind without compromising rain ...BUT...the outdoor temperature sensor then seem inappropriate with no radiation shield, because it isn't truly weather proof and requires to be located in a covered location or in a Stevenson Screen. I've given Ecowitt feedback on this that they should come up with an outdoor sensor with a radiation shield to improve the HP3501 and they said it sounded like a good idea to them...but no word if they will actually do this. I think if the did this it would be a decent system. So that part is holding me back from recommending this separate component setup. Also I don't know if those separate components are capable of being picked up by an Ambient branded console. If you don't have an Ambient console then you don't have access to AmbientWeather.net.....unless you have a Meteobridge with add-on AmbientWeather.net license ($150)...or you have a Meteobridge that is from Ambient and therefore it is called a WeatherBridge which already had this license. Why you would want to be sure you had AmbientWeather.net licensed device is so that you can take advantage of the great Amazon Alexa and Google Assistant integration....if that matters. Also to me I want to maximize the number of networks I can get onto because it is more fun. The Ecowitt.net network only works with the GW1000 and not currently with any of the other Ecowitt display consoles....but they are working on that in some future upgrade. Ecowitt.net also does not yet have any Amazon Alexa nor Google Assistant integration.
* UPDATE - March 2020 - Ambientweather.net license for Meteobridge has new lower price, now just $100
Okay so that is probably a lot to process. But if you want to know what I really want....that is a Davis VP3 which doesn't exist...yet. So all this for me is a holdout till that is available....unless Fine Offset and companies like Ambient and Ecowitt keep upping their game and keep improving theses stations. Currently they use SHT30 sensors instead of SHT31 like Davis and Acurite. But one of the things I don't like about the Davis VP2 is that it uses a legacy bus (LSS) and there are known issues with their temperature and humidity sensor after some 18 months or so of operation and sometimes less. That also limits the VP2 from being able to use the newer and better SHT35 or SHT85 which is only supported on the I2C bus. So the infamous VP3 when it does come out better have an I2C bus for me to be happy. The new Davis WeatherLink Live seems like it will have an API that will most undoubtedly be used to create custom software displays with cheap tablets as stand in displays while the WeatherLink Live becomes the one and only console.
Okay I'm getting carried away talking about Davis and you already said that wasn't in the budget. But I just wanted to say that I recognize the merits of the Davis. Like for example the top wind speed on the Fine Offset clone station is only 100 Mph. And the outdoor humidity will only measure a low of 10% RH (limitation of SHT30). Just wanted you to be aware of those things.
Bottom line....for me there is no perfect station today at any price. Makes it hard to recommend anything blindly without knowing what the person is interested in and what is important to them.
But I am very happy with my current setup because it is very capable at least in terms of expand-ability and all that I can do with my data.