New System or Upgrade Q6600?

Ok so i ran into another dilemma about what i want to do. Basically i have this system right now:
C2D Quad Q6600
MSI P31 MOBO (crappy, worst mobo ever)
8800gt
550w BFG psu
Xfi extreme gamer sound card
2gb gskill ram

I can save myself a ton of money if i keep the q6600, upgrade my motherboard to an ASUS RAMPAGE, Buy a 4890(or equivilent) And throw in 2 more gigs of ram. My questions is will i see that much of an improvement in games if i build a new Phenom 2 955 system? Said an done im saving myself about $400 if i go this route. If getting a new cpu is only gunna gain me 10 frames then i dont think it is worth the extra $$$.

What do you think?

I think i might just do it this way, plus that p31 wasnt stable over 3.0ghz, so with a good mobo i should be able to oc it higher, in a way its like having a new cpu haha

I do gave G0 stepping, and i have an arctic freezer 7.

Yes it will work great! I would get the 4890 $229 or gtx 260 maxcore bfg $179, get 2gb of ram, and a p45 motherboard.

For crossfire no.

Wait, what? in all benches I've seen the x48 board can oc further and it has 32 lanes instead of 16.

So my 550w bfg should be fine? or should i by the corsair, i plan on overclocking.