SME V vs. SME IV/Vi or Vd

Ok, looking for some guidance on the several iterations of the SME available. Will be used on SME 30 TT with Dynavector XV-1s cart. Major sonic differences between the V and IV/Vi? It's also my understanding that the SME 30 can be purchased with a 30A designation which is the SME V arm. Is this different than a "standard" V. And finally, thoughts about the detachable headshell option of the V. Thanks.
SME 20A or 30A comes with a 'Gold' SMEV which is a 'select' SME V with Gold lettering, whatever it means. IV.V is a special Sumiko version since SME IV and V can be easily found oversea at half the price they charge in the US.
The SME V has a damping trough which makes it more "tuneable". In addition it can be rewired very inexpensively through Incognito or some others. It comes out to be less expensive than the IV.Vi still. The rewire has some specific advantages. First you are using a single cable from Cartridge leads all the way to preamp. Second, you are eliminating the only advantage of the IV.Vi and at the same time, saving on buying a second tonearm cable. Lastly, the SME V is a very good tonearm but if you can get it with adjustable azimuth it would be even better, which is an option.