If you're looking for "tight" bass, I'd stay away from the PRO-900 and the Denons. The best description that I could come up with for the 900's low end performance is that it displays a sort of "bass cloud." That is to say that it's plentiful in quantity, but is often indistinct/dissipated and sounds more like it hangs over the rest of the tonal spectrum instead of staying in the basement where it belongs. On the other hand, the Denons give a nice sub-bass rumble but are generally flabby and slow sounding in the bass department with some intermittent/subtle encroachment on the midrange in extreme circumstances. I haven't heard the D5000, but I think it's safe to assume that it won't be a huge departure from the D2000 or D7000.
A question: what exactly is your budget? You list $700 as your maximum but then go on to ask about the Edition 9. Given I haven't paid much attention to it in quite a while, but does the Ed9 actually go for that cheap now? If you're staying with Ultrasone, you may want to stretch your budget a bit and pick up a used Edition 8. (a few have been on the FS forum over the past few weeks for <$750) Bass is both incredibly strong (only when beckoned... it doesn't "inject" bass into content where it isn't present) and among the most articulate I've heard. I haven't auditioned them yet, but there are many happy Edition 8 owners that are now touting the Signature Pro as an upgrade as well. ($850 new at RMC Audio) If you want a taste of the Ultrasone sound instead of going directly to the top of the food chain, I really can't recommend the HFI-580 enough as a budget can. (around $100 used) To my ears, it's an upgrade over the PRO-900 in every way (especially bass articulation and it curbs the nasty, metallic treble) save for comfort and perhaps soundstage size. I have zero experience with portable amplification in general, but all of the aforementioned 'sones will run sufficiently well directly out of your source and allow you to "scale up" your sound (not tremendously so with the HFI-580, mind you) when you decide to invest further into your audio chain.