They are good amps, especially the power-amp stage which uses a pretty hefty transformer. You can run some fairly tough speakers and the Denon will still cope. I remember the amp being smooth and controlled, never bright. It was almost like a stereo amp that just happened to have an AV decoder in it. The processing is not that good by todays standards, but it is the implementation that counts, rather than merely processor specs. IMO I preferred my old A10SE to something like a Pioneer AX5 which had "better" processing and more features, but lacks the overall class of an A10SE. The only things I didn't like were the remote and a tiny little volume readout on the front which you cant read properly unless 2 foot away from the amp. There is certainly better out there, but nowhere near the money you paid.
Movies sound great, but more importantly I am totally confident in its ability with stereo material. One final point, you won't get anything like the build quality with any model you get for your 450 notes. Just make sure you don't hurt yourself lifting out of the box.
it doesn't have HD video capabilities but then I have never used the amp to switch video sources, these have always gone straight to the TV. It also doesn't have the latest Dolby and DTS decoders (but it does 7.1) and let's be honest, trying to get acceptance for 5.1 is bad enough in the lounge, anything more is just a non-starter with most spouses!
The THX adds some more oomph to soundtracks and the flexibility of the digital inputs is great.