The i5 750 is a quad core processor, while the i5 650 has two cores (but these cores are multi threaded so to speak to give it 4 hypothetical cores).
Darn. And right after I thought I had finally figured out the intel naming scheme:
i7=HT and 4+ cores
i5=no HT and 2 or 4 cores (now proven wrong)
i3=HT and 2 cores
Looks like I'm going to have to start all over again