I would assume you intend to order from newegg and that you plan to purchase everything you just listed. So I just need to ask, why would you purchase a Q9550? It's listed at $259.99 on Newegg and a Phenom II 955 is only $171.99, they swap blows with one another and are essentially equals in terms of performance. Socket 775 is also a dead end with no new processors, while AM3 will have X6 processors in 2010 and Bulldozer in 2011.
You could also get the I5 for $199, and budget that other $60 for a socket 1156 motherboard and have a more powerful system.
Either way, the Q9550 has terrible price/performance now.
From what i see, The OP has this computer currently but just use a newegg link to show what motherboard it is. All he asking if he should upgrade from the motherboard he has.
I agree with JSC. You can get the motherboard he listed or save up to get an P55 system