From: Running car amp in house off of PC PSU

[JimJ 11]

You would be better off with a motorhome power inverter. Some of these convert 110V into 12V @ 40 amps or something like that. It depends on what type you get. These can be found at any RV repair shop for under $200.

True sine wave inverters for that price?

He'd need to stay far away from anything with a square wave output. I know true sine wave-capable inverters are out there, heck Radio Shack used to carry them back in the days when they had a catalog, but I don't remember them being very cheap.