A few comparative comments for you:
I have a Woo 3 in my office, and a modded Crack w/ speedball in my main rig at home - both running well regarded tubes (specifics in profile). While I certainly still enjoy my Woo (on a daily basis, in fact), the Crack is the better amp. I found this to be true even when my Crack was still in stock form. It is simply a more detailed and dynamic amp, with a better defined bottom end.
I haven't had a chance to hear the 600 ohm Beyers with either amp, but the above holds true with all of my high impedance cans: HD800's, 650's and DT880 (250 ohm).
This is no knock on Woo Audio. I've heard every amp in their lineup, excluding the new reference monoblocks, and they make wonderful gear - especially their high end stuff! The Crack is just an absolute steal even after the minor price bump. Also, FWIW, when considering cost, nice nos input tubes for the Crack (like clear tops and bugle boys) can be had fairly cheaply on ebay. Premium tubes for the WA3, like the 7308 pq's I'm running, are selling for pretty absurd amounts these days.