I've been eyeing/lusting over the WA7. It seems like a simple and elegant solution that takes up minimal desk space. I've only seen one comparison and the WA7 outclasses the Bifrost/Lyr but not by a lot. Don't think you can go wrong withe either given that they're roughly within the same price range. If this is true, I'm thinking of going the WA7, get both sets of tubes and then be done with it. The Bifrost gives you more flexibility but I'm OK with a USB only solution.
I was actually under the impression that the shiit stuff was far more expensive than it's now looking, it sounds like that might actually be the way to go..
the Fireflies are such a beautiful solution though! and so neat :) I may end up going with the WA7 with the Russian tubes (better for electronic they seem to be saying) and see how I go, if it's not enough then move to a shiit stack