Really, it depends on your budget. If you don't care how much it is, you have about a billion choices for high quality oxygen free copper wire. If you're on a budget and not running more than say... 3k, copper clad aluminum is cheaper.
Check out this thread and you can see some pics. KNU is very popular around here. Shok is one of my personal favorites and they just came out with a hybrid OFC/CCA which is still affordable. And XS Power has a very nice product for a good price.
Most would agree that Cadence is one of, if not the best "bang for the buck" stuff.
With all of that said, I still use 2/0 flexaprene welding cable for just about everyting.
Post your wire pics.