A 15-20% increment would be quite fair tough; however I got the feeling that the new 3806 will have a direct opponent; i.e., the heavy-weight Yammie 4600, rated @ $1,900. That is a step higher than the current 2500 / 3805 ranges.
What makes me believe in the above, is the fact that the same way the 3805's are riviling the 2500's, the 3806 will be doing the same over the 4600.
If that theory is correct, Denon will have to add more power and several extras on the 3806, in order to justify a $ 1,200 jump to the $ 1,900 level.
Knowing Denon's price policy, I'd bet their MSRP will be a bit higher than the Yammie 4600 - UNLESS - they decide to change their policy and compete directly with Yamaha on an inch-by-inch basis (not usual).
If we analise the whole thing - Yammie is indeed the best bang for the buck on this price range (2500 against 3805 = cheaper, + included mike, more power, THX badge, more dsp's...).
Let's see what their strategy will be.
Cheers / Avliner.