Phenom 550 vs Athlon 620

Athlon II X4 620 and Phenom II X2 550 BE compared

Both CPUs will overclock with stock CPU coolers:
~3.7GHz for Phenom II X2 550 BE
~3.2 for Athlon II X4 620

If you need 'the most powerful with the best performance' there are better CPU choices if you can spend more than the cost of the Athlon II X4 620 and Phenom II X2 550 BE. Phenom II X4 965 Black Edition Deneb 3.4GHz
If you want the most powerful $100 CPU I'd say get the Phenom II X2 550 BE.

I've been fairly impressed by the performance numbers for the AthlonII x4 620 considering it's a $100 CPU. Here's another recent test along with overclocking numbers.
http://techgage.com/article/amd_at [...] ore_at_99/