I got my Legacy GT which has the same performance as the spec-b for 24k. Same car minus the revised shocks and wheels... and color of leather. The MS6 is a coppled together monster 6. The subaru was designed from the onset as a 4wd sports sedan. The MS6 is a preformance joke. There are tons of posts from owners who are complaining because the car isn't performing like it should. Look at the latest comparo with the MS6 against other AWD sports sedans. The engine ran out of steam and had the same 0-100 number as a toyota camry 4 cylinder. There is heak soak and octane problems... it makes less HP then the suby when you put 91 in it and after some agressive driving it turns the boost off. As mentioned before the awd is an afterthought. The spec-b should not be compared to anything since they only made 500.... you are better of comparing the Legacy GT Limited since its the same car minus the wheels and the bilstein shocks.
The MS6 is a cool car but needs some revisions before I would trade my Subaru in for it.... think reliability down the road also. The interiors are too close to call. Drive them back to back and then decide.