graphics card and memory problem..help...?

i recently traded my crucial ballistix tracer to corsair dominator. same speed and size, did i made the right choice? both are 2x1GB ddr2 1066. i'll be using it for my new motherboard, msi p45 platinum. is this a good spec for my gaming rig?

intel core 2 quad q6600

msi p45 platinum

msi ati HD4850

2x1GB corsair dominator ddr2 1066 (used to be crucial ballistix tracer)

Hec winpower 550w.

can i play all the latest games with this specs? i'm also planning to add another card for crossfire.

thanks