what makes u think a hd 4850 is not good enuf for a hd lcd..
am usin the e2200hd....
i game on full 1080p on high settings...done playin mirrors edge ... cod 4/5 widout a glitch..
dmc 4 /grid / pure 60fps avg on full hd.
bioshock./ fallout 3 / hawx...runs great..all high or very high...
u need to customise gta to suit urself..and crysis gives arnd 30-35fps full hd on gamer settings...
i still havent oced my hd4850 ...now runin at stock 625 core clock....but can give even better peformance if u oc it to 680-690...
so i suggest u get a full hd lcd..now tht its cheaper than ever..and also makes the movies look awesome..