Whatever you do, if you want to learn how to make great sound from your system, I strongly suggest that you only change one variable out at a time! - otherwise you'll never know where you're really at!
I'd say that the biggest change (besides acoustical upgrades) would be the speaker change. If, overall, you like the sound of your current speakers, then I'd say try another amp, pre, cables, etc, yes. If you're not thrilled, the speakers will be the biggest change. Then, if you like the speakers you're working with, THEN try other associated gear, wires, power-conditioning, etc.
I say, if you got the upgrade itch, and you want to try the Quads, I recommend you follow that seed, and see where it takes you.