Hmm, Scythe Ninja has gained a fairly fearsome rep. It was designed as a passive cooler, but with a 120mm fan or 2, it's right up there with the BT. The Tuniq Tower is a somewhat recent creation but tests have shown that it's way up there too.
You can buy the Ninja here
I did a quick search on the Tuniq Tower on Froogle for the UK, didn't turn up any results. Here's
the manufacturer's site if you want to check it out.