If your running them stock and not overclocking the 6000 is slightly faster, if your overclocking the 6550 will overclock better and outperform the 6000
Phenom is AMDs new processor coming out later this month, its a quad core Phenom X4 Agena then later probably next year a Phenom X2 Kuma and later a Phenom X3 Tri core
No the Phenom will be there top line processor, the Athon will be demoted to there mid line processor. If you mean between the E6550 and the X2 6000 the 6000 will be alittle faster stock.