The A8 is NOT much worse. It is in fact BETTER than the FX-4300 if both were at the same frequency as it's a slightly newer design (not by much). So for all intents here they are IDENTICAL PERFORMANCE.
FX-4300:
http://www.cpubenchmark.net/cpu.php?cpu=AMD+FX-4300+Quad-Core
A8-6500 (CPU only):
http://www.cpubenchmark.net/cpu.php?cpu=AMD+A8-6500+APU
So the FX-4300 scores only 3% higher at 4GHz Turbo compared to the A8-6500 at 3.5GHz (no Turbo). So next time do a little more RESEARCH...
Your Phenom 955 for comparison scores 4012.
*Having said this, every AMD sucks for per-core performance so a "true" 4-core is a recent Intel. The i5-4670K for example gets 7736 which is about 63% better than the FX-4300 with the same number of physical cores. Ouch!
This also helps explain why the 2-core G3258 beats the 8-core FX-8350 in Skyrim as the game only uses two full cores roughly.