Look at the Feser 4x120mm radiator on FrozenCPU.com. Probably the best 4x120mm radiator out there, for $80 - 5% promo code + shipping (it's so cheap because it's being discontinued).
As for websites, I use sidewindercomputers.com and koolertek.com.
Well, there's your quad right there, a lot thicker than most other quads, but that is what makes it one of the best.
Look at the sticky in this forum, they did a roundup of triple radiators. Look through them, check out their prices (once again, koolertek and sidewindercomputers are my recommendations), and choose which one you want.