Nearly all modern computers will easily play Trackmania and Wolfenstein.
Requirements to play Model2/3 and PSX2 emulators
CPU High 2 GHz with SSE2 support. (A decent mid range CPU)
Video card that supports Pixel Shaders 2.0. 8600gt or better. That's a low end $25 video card. Nearly anything more than a generic onboard card will do.
A large hard drive or a dvd burner.
2GB RAM is enough but go for at least 8.
Some computers that will work
Dell Precision T3500 Workstation Desktop Xeon W3565 3 2GHz Quad 12GB 1TB HDD | eBay
Dell Precision T3500 PC Desktop W3550 24GB 10600U 500GB HDD NVIDIA Quadro 4000 | eBay Needs OS.