I am trying to get an old extreme budget build off the ground for my nephew who wants to get into pc gaming, but currently only focuses on games like Minecraft. I figured building up an old low profile HP tower would fit best for this occasion, but I want the rig to have a quad core cpu rather than the triple core Phenom it has now. Since this system has an AM2+ motherboard, what is the best quad core phenom or phenom II I can slap into it?
My knowledge doesn't extend far enough to give you advice on that platform, but do remember that Minecraft is HEAVILY CPU-bound. Even something like a cheap, recent dual-core pentium would likely outperform anything on the AM2+ simply because of the higher per-core performance.
AM2+? That wasn't a good platform for home use from what I remember and was a lot better for offices and schools. If you could bump up to am3 I could recommend a phenom 2 955 BE. My chip is right on the edge of way too slow and I stream. You might want to go up a level here.
a lot of am2+ boards could run deneb phenom IIs even some am2 boards could. Deneb quads and Regor dual cores etc could use ddr2 or ddr3. I used a phenom II x4 945 95 watt on an old asus m2n32 sli deluxe board for a while just depends on the motherboard bios.