I believe Mwilson is correct, the Quicksilver preamp is definately not the limiting factor. It is capable of throwing a very large soundstage. The sound produced by the Quicksilver is slightly warm but with very good detail. My only caveat with this linestage is that tube rolling only produced suttle results.
B&K makes some excellent products for the price but like most midfi manufacturers, not every model delivers the same results. By the way, one of their newer preamps like the PT3 is a screaming bargain but thats another story. If very good soundstaging qualities are high on your list you should try pairing the Quicksilver with a McCormack amp. I have done this with an excellent & satisfying outcome. Also McCormack amps and Vandersteen speakers are known to sound very good together, Steve McCormack himself mentioned to me that many of his customers who owned Vandersteen speakers were very happy with this combination. Or you could look for a Quicksilver amp which will offer alot of synergy and take some of the guesswork out.