dont know if your games console clued up??
if i was you i would go into your local gamestation.
they do trade ins, so you could take in any old games he doesnt play anymore and use that against your purchase of a second hand ps3.
thing is the games are on both formats xbox & ps3 bar the odd few, so the only major advantage to getting a ps3 and already owning a xbox is the ps3 has a blue ray player built in - much better picture than standard def dvds...