Nice system. should do 3.0ghz easy.
For video if your are not gaming. you may want a 7600GT(so you at least have some power)
or 8600(for its video acceleration, but your quad will do it all for you if you want. This card is not recommended for games.)
The Deluxe accepts more SATA devices, has wi-fi, more RAID types, better onboard audio and S/PDIF output, and yes apparently it's easier to overclock. I would probably get the Deluxe, even at $100 more. I read that the P5K overclocks a bit better than the GA-P35, by the way.
I've never used Mushkin RAM but I hear it's good. Lots of people here like SuperTalent or Corsair too. I have OCZ and it's fine. I'll let the experts handle this one.
Edit: how about GA-P35-DS3P, this one has FireWire.