The difference between 955 and 810 is that there’s a 400MHz difference in core speed and 2MB less L3 cache on the 810. If you are going for a quad core for just the no. of cores, get the Athlon II X4 620/630 instead. It is a great value for money. Only thing lacking here is the L3 cache. Or if you are going for it for raw power and can afford it, then go for the 955. 810 is also a good proc at its price point but it is just the middle ground. And as for the Intel procs, as you’ve said yourself, Intel has a super confusing set of sockets which are not compatible with each other, let alone previous generation. And going for Intel would mean locking yourself to that socket and denying yourself the opportunity to upgrade later