I still think a decent sm psu rated at 144w 20-30v ~7a works great, its what I use and I can run 2 3s packs on a 610i duo, with next to no sag costs like 40$ shipped on ebay and just need a for + nad -.
Hers one for folks who need lots o powa
http://cgi.ebay.com/Mean-Well-SE-600...3A3%7C294%3A50
wow theres a lot more power supplies on there now that are 24v 3a-25A just do an ebay searh for power supplies and look for ones that like the one above, especially if you get a hyperion charger I think most of them can run from 12v-28v, I run mine at 26.6V and i have no problems.