I would personally like to recommend you look into something other than powered speakers.
Get something such as this Dayton 50w mini amp.
Maybe power a set of Polk Monitor 30's (to start, you can always add better bookshelfs later with a good amp such as the above). This would also allow you to EASILY add a subwoofer to the setup later if you chose to do so.
I think the question I should ask then, and an important one, is this: would the QUALITY of bass (and mids, for that matter) differ enough from the M10s/Promedias that I should strongly favor them over the Swans/Rolands?
Bass quality is what I know best.
I don't know anything at all about the M10's or most of the powered speakers that you've listed.
But the ProMedia's as a great example....
They are solid multimedia speakers. They have great low end response, decent mid range, and excellent treble. They sound "bright" so to speak. The subwoofer is directional, which you will find that happens with ANY subwoofer that is paired with such small speakers. Directional sub is bad. You shouldn't EVER know that a subwoofer is present in your system by just listening to it.
Pick either a seperate amp + passive bookshelf setup (that has decent full frequency range down to 50Hz at least). Preferrably 5.25" or 6.5" woofers on them. The bigger, the better the low end will be. If you don't ever, EVER plan on adding a proper subwoofer later, then go ahead and find some solid active studio monitors. But if you're wanting bass response out of them, you'll want them to have somewhat larger woofers (5.25" - 6.5" at least).
Your speakers, being full range, should reach down to roughly 50-60Hz successfully. I can personally tell a directional subwoofer down to around 60Hz in the right environment. So 60Hz is a good safe point for cutoff for your subwoofer (possible to add later).
Keep in mind, you may get "flat" response out of active monitors. But that flat response is only good for the frequency range that those small drivers are capable of. Which means you WILL be losing out on pretty much all of the low end (20-80Hz roughly). Even the ProMedia's won't reach proper low end response, but they are certainly better at it than most.
Hope this helps.Edited by pioneerisloud - 3/20/11 at 6:02pm