It was a lot cheaper in my case as I bought the 2808 on the Richer Sounds VIP deal of £399 and I already had an older NAD350 stereo amp to power the fronts. This takes some weight off the 2808 as it then mostly needs power for the centre and then the surrounds to a much lesser degree. I have a reasonably sized lounge of approx 4 by 6 metres and being detached I usually watch films on my PJ with the Denon set to -15 on the volume and it's plenty loud enough even though my speakers aren't necessarily the most sensitive or easy to drive.
I'm not sure about the differences with the 3808 having better DACs, but the 2808 still has AL24 plus and the Prologic II, Dolby Digital & DTS decoding sounds good to me (and that's after a 3805 now relegated to my conservatory as it's not worth selling

). I've not got a True Dolby HD /DTS Master source, only PCM from my Sony BDS-300, but with the film '300' & on other PCM sound tracks (which can be 'upgraded' to 7.1 using the appropriate setting on the 2808/3808 BTW) it sounds more than good enough to me. I just enjoy the film and don't analyse the sound anymore.
The only things that you'd loss out on are the network parts of the 3808 if that bothers you and 2 less HDMIs, apart from the DACs and power rating that you already mentioned.