I have been running OCCT that puts the CPU under stress and if I don't overclock it, the system seems, so far, to be stable.

I will probably upgrade my processor from the Athlon X2 Kuma Black edition 7750, any suggestions/advise welcome.

I think I will go with the Phenom II X2 550, review looks good (I assume this to be the AMD X2 550 in the tests:
http://www.fudzilla.com/content/view/13975/40/1/2/