What do you plan to use your system for? For gaming an i5 750, AMD Phenom II 955/965, and any i7 will perform very similarly. If you arent gaming there is a bit more to consider. If you plan on doing some video encoding or a lot of photo editing then the intel processor will be slightly better, but for general use, web browsing, movie watching, etc, one of the lower i5s or an Athlon II x4 is more than sufficient.