AMD Phenom II series

[CacoFFF]

Now, what kind of memory do you want to use?
DDR2 or DDR3?
If you're going for DDR3 memory, socket 775 won't take much advantage of it, so anything AM3 or Core i5 would be your choice.
If you're planning to buy DDR2 memory (or already have it), then the choice is entirely up to you.