BFL's single uses 72W at the wall, there is no ATX psu or DC/DC or extra for fans etc, just the host usage to be added. All speculating of course coz it ain't alive yet, but it is definitely no 620W, or 108W.
Yes it's all speculation. At the moment BFL is paperware which uses no power at all and produces not a single hash. Let's wait if they manage to release an ASIC product at all and after that, let's see what their power and hashing values are. At the moment Josh started with his pre-delay anouncements so don't expect a release soon.
Back to Avalon, will they open the source code or at least provide the sources to their customers?