YellowJacket said:
The most sought after version of the 2 channel recto is the Rev C and D, which are roughly the first 600 Rectos that were built. The Rev E and F are also good amps but since there are more of them, they are less valuable.
Not of Rev E, it is in fact the rarest 2-channel revision. Only about 100 were made, their serial numbers run from a little over 500 to a little over 600. The first 500 or so were Rev C and D.
It is debatable whether the E should be considered a "pre-500" revision, certainly not by their serial numbers, but because of their sound. Because of their rarity, few individuals have had the chance to A/B test an E and a C or D. (I haven't.) But based on what I've heard and read, the E would be sonically closer to a D than to an F.
As for the European going rates for Rev G Duals, I would take a look at the asking prices and closed deals on ebay.de and ebay.co.uk. There will probably be some variation per country. I would guess that 900-1100 or 1200 euros would be an ok price in Belgium, and certainly wouldn't pay over 1300 euros.
Oh, and don't sell your 3-channel Rec before trying the G first. While it caters the same core sound, more or less, its feel will be different. It is darker, smoother and warmer. It may have less 'fizz' than the 3-channel Rec, but you have to tweak your sounds a bit to have the same cut live.