Phenom x2 550 vs intel core 2 duo

The Intel and AMD aren't running much from each other. but i can say the AMD is a lot more Stable and also if you get lucky, you can get the 3rd and 4th core unlocked on the 550.
 
The Core2Duo E8XXX series is faster than Phenom II, but at a much larger cost while being on a dead end platform. If you buy a Core2, you won't have anything better to upgrade to later, and both AMD's socket AM3 and Intels socket LGA1156 have better price/performance offerings.

I'd recommend going with Phenom II, or I3, forget about Core2.
 
The other thing you have to consider with these two processors is the socket type. LGA775 which the C2D will have no more new CPUs made for it making it a (near) dead socket. However the AM3 socket which the Phenom II uses is AMDs current socket type and should guarantee you that little bit more of an upgrade path in the future if you need to upgrade again. Just a little something else to think about if the differences in performance are marginal then this may be an important point to consider.
 


Got there before me 😉