If you don't plan to overclock anything then a good quality 450w psu should be fine. If you do plan to overclock that Phenom II 965, it will use alot more power and I would recommmend a 5-600w PSU. If you did grab a good quality 600w PSU you would be fine to overclock and upgrade your video card in the future. At least you wouldn't have to replace your PSU all over again that way.
Corsair, Antec, XFX, Seasonic, PC power and cooling, are the brands you would want to look at for a quality unit.
http://www.tomshardware.com/reviews/phenom-x4-965,2389-10.html System using the Phenom II 965 at stock and overclocked, using a pretty power hungry video card(4870x2). Your 7770 will use about 1/3 of the power the 4870 uses, but as you can see if you add another card or go for a higher perfoming video card a 450w may not be enough. 600w to be safe and a little future proof, is my recommendation.
PS: A PSU is likely to last longer and be more efficient when you have a little headroom to spare. It's not a good idea to load a PSU close to it's maximum output IMO. The newer intel chips use far less power so you can get away with a smaller PSU, but AMD's chips have some catching up to do in total power consumption. Especially when overclocked.