I upgraded from 5's to 5A's and found the differnce to be tremendous--well worth the cost (I had early versions of the 5's so it was over $5K for the upgrade). From top to bottom, it's a significant improvement. The 5A's offer much better detail, with noticably lower distortion and less listening fatigue. At first it seemed as though the 5A's were less bright, but you soon figure out there is no differnce in brightness, just lower distortion in the upper midrange and high-end (richard told me the distortion has essentially been reduced 50% in the 5A). I agree with Will, that the bottom-end is more extended and defined, but for my money/taste, the improvement in the midrange and high-end is the most pleasing aspect of the upgrade. I also had the speakers refinished to high gloss for another $1000 while at the Vandersteen factory, and the improvement in cosmetics is well worth the price to me (mine were standard walnut, not too great looking before the finish upgrade). I plan on keeping these speakers for a long time.
One note, although the 5A's were noticeably improved when I got them unpacked and set-up, they do improve significantly once fully broken-in. Richard tells me it takes 200 hours to fully break-in the new drivers.
My asociated equipment:
Levinson #380S Preamp (w/ PS Audio Radian Power Cable)
Levinson #360S Processor (w/ PS Audio Radian Power Cable)
Levinson #37 CD Transport
Levinson #335 Amp (w/ PS Audio Ultimate Lab Cable)
PS Audio P300 Power Plant (on source components, with PS X-Stream Plus Power Cable)
Transparent Ultra Balanced Interconnects
Transparent Ultra BiCable Speaker Cable
PS Audio Power Ports and 20 Amp Circuit
Lee Allen