DX10 and DX11 mostly improve on lighting and shadow effects. Such things require more elbow grease to program for (lighting object locations and angles, shadow depth and intensity, and stuff like opacity and obstruction). So just switching up to DX10 without that extra programming isnt going to make the game look much better.
@BroTranquilty
Which games have you played that only work on x64? I cant say about Planetscape 2 since I never played it, but I dont think Ive played a single game recently that even had a 64 bit version, let alone not include a 32 bit version. Im mostly just curious, since most OEM computers shipping these days still ship with x86.
And Windows doesnt use much background power aside from an increase in RAM usage, but if you dont have 4Gb of RAM nowadays, Id say your computer was something like 5 years old. Graphics and CPU processing power is hardly touched by Windows after the initial boot.