On Windows, each Core 2 Quad should give you between 5000 and 8000 points per day. The Phenom X6 won't be able to run the bigadv units under Linux because you need to have eight cores to get those (or at least eight virtual cores). So you'll just be able to run the standard clients and compute standard units on all your machines. Assuming the systems will run 24x7 and that you'll have three computers (2 C2Q and 1 Phenom X6), you should still be able to contribute at a daily rate of at least 15000 points, maybe closer to 20000 points. That would help us a lot. That would put you toe to toe with P5_133XL. For reference, this month (excluding today), Mark average 17692ppd while I did 23 876ppd.
What operating systems will you use? Windows XP 32bits, Windows 7 64 bits, some Linux flavor on one system?