I've tried them in Billet Box (with Billet Bridge) and a Viva Nova (I think that's what the name is - either Viva or Nova, I get mixed up, why did Aspire name their tanks after old Vauxhalls? Showing my age... Ah, just read, it's a Vivi Nova).
In my opinion, they're a big improvement on the BDC which they replace, certainly in the Billet Box, and getting rave reviews on the ECF Billet Box thread. I can't say I noticed such an improvement in the Vivi Nova, but that may be down to the juice or that particular head.
On Fasttech, boxes of five are $7.88 (choice of 1.6, 1.8 and 2.1 ohms). I bought five 1.6's from UK ebay, but seller seems to have disappeared now.