You might be able to find a Geforce 750 for $125 or so. They're adequate but definitely not ideal for 1920x1080 in most PC games. They're also ridiculously efficient; they don't even need an extra PCIe power connection.
If anyone tells me they want to game on a PC and don't immediately mention a game with a more serious demand, that's the hardware I use.
I generally prefer ATI hardware because I think nVidia's stock cooling kills graphics cards and I'd rather deal with crappy drivers, but the current ATI hardware is a complete non-starter. There's really no level at all where it can be justified.