What application do you usually do?
Get Q8400
More and more applications are optimized for hyperthreading, 4 cores would be super beneficial when you work with video, in gaming it will be 50/50 - some games still like dual cores with higher clocks. On the side note E8400 might be easier to overclock - lover temperatures and higher multiplier. Is it possible to get i3 540 instead? It'd dual core but with hyperthreading and turbo-boost, I think I would go with this one, little cheaper, enough for DDR3 upgrade and P55 or H55 mobo
I don't think i5 650 really worth the money when compare to core i5 750
My current list on cpu would be
Athlon II (any which suit budget) < core i3 530< Phenom II x4 955 < core i5 750 < core i7 860 < core i7 930