1. Won't severely hinder performance of AMD Radeon HD 7750
2. At least 3 cores would be nice, but not neccesary
3. I'm not rich, so don't go recommending Intel Core i5's because I know I don't need to spend the money on it... unless you find a really good deal
I already own an AMD Athlon II X3 455, but might sell it if it isn't powerful enough.
well the pentium is a dual core with no hyper threading so defeats ur needs there and a i3 ivy bridge or sandy bridge has the hyper threading which when used is dual core 4 thread, and a phenom ii x4 965 is a native quad core and costs less than the i3s and prob only $20-30 more than the x3 u have and better than an athlon x4.
On newegg ur 455 is $75, same pricing as the pentium, and a IB/SB i3 is around $130, and a 965 is $110, even an athlon x4 is only $5-10 more than ur current 455 x3