I'm using Rosewill 10-port powered hubs. They seem to have no problem powering 6 or 7 sticks (7 on 2 of them, 6 + the Pi on another).
i've got this Rosewill hub on the way... good to know you've got yours to work!
http://www.amazon.com/Rosewill-10-Port-High-Speed-RHB-520/dp/B007ZSKJV0
it's a 3.5A, so i think 7 erupters would be a hard limit
