just email them. I think everyone will agree that Nik is awesome to deal with, and knows a lot about his products. I'm getting the 1986 bass plexi, and we discussed many different options (and sooooo many emails, and Nik is always polite and helpful), and this seemed the most appropriate..
Also, as Nik suggested to me, go out and play a bunch of the vintage versions if you can. You'll get a good idea of what sound you want from that. I tried the 1987 plexi, but found it a bit bright, which is how we got onto the bass plexi.
Besides, how much fun is it playing a bunch of really expensive amps you have no intention of buying, eh?