I'd like to add two somewhat disparate thoughts to the excellent comments above.
a) The recommendation by your dealer to use Basis as a source may be very well grounded in fact, with Basis possibly being a proven, synergystic match with the Vandy's.
I listened last week to a pair of Vandersteen 5 Carbon's that were sourced by a Basis Turntable and powered by ARC signature amps. I'll spare you the platitudes except to say that the result was mindbendingly good. Actually, both Vandersteen rooms had Basis source and ARC amplifications.
I also (after meeting Jim V himself!) spoke with one of the ARC owners who described how ARC and Vandy, and to a lesser extent, Basis, have been used together and have presented together for years.
Not sure what other (sonic?)issues there are, but at least the form factor for all of the 2000 series and above seems at first glance to be very much the same.
b) With your system quality and budget for source component, please do not assume that you have heard anything near the best attainable from digital.
Also give very strong consideration to auditioning one of Playback Designs' products, such as MPS-3 CD/DAC that plays 24/384 KHz PCM and 6.1 MHz DSD over USB from your computer. This system was designed from first principles by the legendary Andreas Koch from Dolby Labs, Sony, etc.
If not as good as high-end analog, it's amazingly close.
http://www.playbackdesigns.com/computer.html
http://www.playbackdesigns.com/technology.html