thinking really hard ref Marantz sr8002 upgrade?

Alt of those models listed feature the more advanced Audyssey MultEQ XT so you would likely notice some improvement in audio fidelity; however, a much more noticeable improvement would be achieved using the most advanced Audyssey MultEQ XT32, although the only Marantz model to feature it is the new AV8801 to be released next month. Denon features it on their 4311CI (on clearance) as well as its successor, the 4520CI just recently released. There are dedicated owner's threads for all three of these models if you want to ask more specific questions.

^^^

you do realize that denon and marantz are the same company, correct?

That's your choice, although note that upgrading to the Denon 4311CI for less than what you'd pay for the 7007 would provide for a much more noticable upgrade in audio fidelity .... again, your choice though. We don't cover the Marantz models as well as the Denon models, so you'll have to do your own research on which Marantz model provides the features you want, otherwise, you can compare the Denon models in post #2 of each of the XX12 and XX13 Owner's threads linked in my sig.