well,about dx10,I would really bother thinking about it-just take a look at todays games,they are only starting to use true dx9c code-dx10 is waaaaay too far away in the future.dx10 games are not going to happen anytime soon,and by dx10 games I mean REAL dx10 games,not just some lame patches that will add a bit more lightning to the game if you have vista and dx10 graphics card..
vista-lovers (and haters as well),I would suggest you read this:
http://www.cs.auckland.ac.nz/~pgut001/pubs/vista_cost.htmldid I mention having vista and dx10 installed on an old pc such as yours has absolutely no meanig? oh,I just did

.you are not able to use your 6800 with dx10 now,and you will never be able to.
sorry to say it,but you totally wasted 169euro..
edit: sorry for being extra spicy today,but my adrenaline is extra high,I had a small visit from a little thiefsie fool,and he took one older pc I had over here for repairs,mmmmmm,too bad I know who he is,and I'm going to waste him good,mmmm yes I will,my preciousss..