First are you aware that you need vista to run dx10 there are rumors that xp will get support but that is all they are at the min.
Secondly i know its good to have the latest and greatest at times but i dont think this is one of those times.
From what i have seen on the forums a lot of people think that the currant dx10 cards will not be able to handle propper dx10 when it finally comes out,seems that at the min what we have is dx9 "sprinkled " to quote another forum member(sorry cant remember who but you know who you are if your reading this)
with dx10 content.
So on the whole with the games not being trully dx10 and with the 2900s trump card the tessilation unit not supported yet either i personally see no reason to spend out on dx10 capable cards when you can get a top end dx9 for a fraction of the cost,and remember you will still be able to play dx10 games in dx9 and probably better as well.
Well thats my two cents
Mactronix