Advice on rollerblades? What matters more when it comes to speed: the rollerblade itself or the wheels?

I have been having bad luck with my blades lately. First the bolt fell out so one of my boots is slipping off the wheel. Then the strap broke on this amazing pair of blades I picked up at Goodwill. I have tried buying a couple more used pairs, but they are all terribly slow. My exact question is how important are the wheels. Could I have a cheap pair of blades and just buy some good wheels and be set? I have owned a pair of Bauer (lasted me 10 years) and a pair of used Roller Derby skates (which were fast, I think, due to the wheels-but the strap broke after 4 months). I am sick of wasting my money on blades that are not smooth and s-l-o-w. Any advice would be greatly appreciated!