The 4870x2 is due for launch this week, so why not kill 2 birds with one stone lower cost mobo but with the frills ie as staffsMike has suggested the Abit p35 XE, Q6600 and the 4870X2.
Support for XFire isnt quite there yet but with AMD 's intention of going multi GPU for the top end card driver support will have to improve to stay in the game, pun intended.
Best of luck in your eventual choice.
@ staffsMike "I wouldn't burn Q9550 money on a quad right now, the Q6600 +IP-35 PRO (XE if you like) will be just as good in the long run I think."
Spot on, I have been arguing with a m8 about a build for him. He wants the latest but the 45nm cpus havent been the success that was anticipated by overclockers. The Q6600 still remains for me the best of the bunch.