its not necassary to upgrade NOW...... DX8 has pixel shaders, bump mapping etc. like 9. of course if someone hands you a 100% working 5950 ultra for 100 tt DON'T SAY NO!
the extra IQ dx9 brings isn't much.... its barely noticable unless you STARE at the game for 5 minutes .
wait till next year if you have a Dx8 card NOW. overclock and tweak till then, ATi should have Shader 3.0 cards out then, and the X-800 pro/6800GT you are drooling at right now will be alot cheaper. And by then, there should also be a new line of 'budget' cards .... since it is customary to bring them in several months after the flagship models. maybe a 6600 ulta?