Tech question for the tech guys there :)

Here is the actual system i have:

Intel Quad-Core Q6600
Asus P5LD2-SE-C V2.X motherboard
430W Cooler Master power
4 X DDR2 1024MO PC533 DANELEC -D2D533- memory
a dead now nVidia 8500GT Silent/HTP/256M ASUS video card
2 X SATA 320 Go HD
Pionner 110 DUAL double couche DVD
Elite 330 case

Windows XP 64 pro
Windows XP (dual boot)

It's a 5 years old system, i was thinking about upgrading/changing it when my video card just died. I guess it's time to do something...

So do you think i could keep some parts of the actual rig to put in a new one?

I would like to go for a I7 (don't know which one though)
I would like also 8 Gb memory (and to be able to add 8 more later on), so i know i have to change the mother board as the one i have now is limited to 4Gb.
Obviously i have to change the video card, but i don't know which one. I would like a not to expensive, but with good response in term of preview for Poser, Modo, Reality. I'm not a gamer guy.
Also i would like to go for Windows 7 pro 64. No more dual boot though.

Another question: is it possible to have 2 cpus in one computer? Could i use my actual Quad and add it to another one?

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