Don't worry about it. There are no shipping games that run DirectX 10 and only Vista will run a non-hacked version of it. By the time that more than a couple DX10 games ship, there will probably have been at least one more new card generation ship, if not two. It will probably take even longer for most games to be DX10 and not just a few of them. Bottom line: you'd upgrade again before you'd even use DirectX 10, so don't base a purchase on that alone.
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