FreakyGreek, I use the 2 channel feature often. Its performance in that area was the reason I chose it(SP1.7). Comparatively, its 2 channel performance is at or very near the top of the heap (when it comes to Processors anyway). The truth is, its good at 2 channel but, a good dedicated preamp can better it.
Plinius and B & W go together like cookies and milk. Most B & Ws arent a real difficult load on the amp anyway. So its easy to match an amp with your desired sonic signature. Plinius has a nice smooth top end, and a tube like mid range, with respectable grip on the bass. I am seriously considering this brand myself. I havent heard much Linn stuff so I cant comment here. It seems quite popular though and thats usually a good thing.
Paired with the right electronics B & Ws can really sing and the SIgs are just that much better at it. Theres a good chance your gonna like 'em.