well, AA (anti aisling) smooths out all the "jaggies" in the graphics. this is not a big deal to many as games take a performance hit for it and for many the benefits are not readily apparent. however the overall affect is more refined (less "rough") with smoother looking surfaces on a whole. it gets rid of the "shimmering" many game surfaces have that are actually many tiny jagged lines. at higher resolutions some say AA isn't worth as much, but i like to run it when i can
big difference between a 8600GT and any 8800 series card. or the 9600GSO. i can't tell you the tech details exactly, but the 8600GT is just a much lower performing card. it has less memory, less "shaders" and is a lot slower. i know, i used to have one.
it plays older or less demanding games fine if thats all you play, but when coming up against some games, meh. Bioshock, COD4, Stalker.....all high settings but for me only at 1024X768 with no AA and i still had some lag. Crysis? played it on medium, on high was unplayable.
the lowliest 8800 (8800GS, same as 9600GSO) can play all these games on high and with the exception of Crysis at my native res of 1440X900 and with full AA with performance to spare. its like night and day.
check my specs they are similar to yours. the 5600+ is only around 10% to 12% slower then the 6400+, so i figure you may get similar performance, although i have Vista so yours may be a bit better.
so i'm just sayin', in your first post you said you had "lag." well, even if all is well and fine with your computer, depending on the game, you may still have lag. the 8600GT is half decent, but one of the cards i mentioned will more then double its performance all the while playing at higher resolution and higher settings....and for not much more money.
just something to think about, i suppose. graphics cards are esay to swap out later....however if this is a new compuiter, just built, no reason not to spend just a little more for a lot more performance.
EDIT: only a couple companies make the 8800GS. if you go with it get an evga model. the other model, XFX, is hella' noisy and the fan cannot be adjusted.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130333
after rebate its pretty cheap. and yeah the rebate comes
here is a 9600GSO:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130356
same card, so why pay more?
another GSO:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814134046
cheaper, and with a more reasonably sized (single slot) heat sink.
the evga 8800GS i linked is factory overclocked. regular version is just $5 less, so....
and finally, an 8600GT (your card) just $25 less after rebate for A LOT less performance:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130341