What you want is a couple B800s. But if you can spring the extra $80 / head for the B1600s, you won't regret it.
Are you sure? The B1600 has a 640 Ws max like the Einstein, but only a 6-stop (vs. the Einstein's 9-stop range). The max power is great for overpowering the sun outdoors, but in a small indoor space like the OP is talking about, depending on modifiers used, the min power of the B1600 may be too much. I often need to dial my Einstein down by 7-8 stops indoors.
Another option is B1600s plus a 2- or 3-stop ND (assuming one doesn't want to stop down to f/22).
Well, even with the B1600s, I've gone close to minimum power but never actually wished I could cut it further. And I do
frequently use my Einsteins at or near full power when I'm using them to light a seamless white background so as to blow it out. And I generally shoot at f/8, sometimes f/11.
I suppose there might be setups where they're too much, and I suppose there might be styles where such setups are common...but they're rather different from mine.
But, of course, the Einsteins are awesome.
(Sadly, there was an incident late yesterday afternoon...a stand tipped and one of the un-modified Einstein fell flat on the Pyrex cover. It'll need to meet its maker for resurrection, but I'm sure I'll be out of pocket well under $100, and that'll include the loaner. PCB service is awesome -- it's worth buying their gear just for how well they take care of you!)