I used a toaster oven to reflow some bad soldering on a Playstation board once. There was a known issue with the GPU chip that would cause the unit to malfunction as the GPU temp increased. It worked well. I monitored the temperature with a probe and temperature meter and just used the oven's normal temperature control.
I think that it would work fine for amp board assembly. Truthfully, I would find it quicker to manually solder the SMD chips in place rather than mess with the solder paste, chip placement, monitoring the oven, etc.
The logistics of such an operation could be daunting, though!
I've also used a heat gun for reflow soldering. Touchy business, but it does work!
Don