I ended up buying a pair of Paradigm Monitor 5's and a CC-370 (V.4s).
I spent a good while auditioning the Atoms, Titans, Mini Monitors, & Monitor 5s. The Atoms sounded a lot better to me than the cheap Advents that I've been using. The Atoms sounded more natural in the upper frequencies and extended more into the lower frequencies. Even though I have a Velodyne CHT-10 I wanted speakers that had resonable bass output on their own.
The Titans sounded better to me than the Atoms because they have more bass output. Since bass is what I felt I was missing the most from my old speakers, I leaned towards the Titans. I think the Titans are probably better than almost all speakers that come with a HTIB (at least all of the ones that I've heard).
The Mini Monitors engaged me more than the Titans. The difference in the tweeters in the Monitor Line vs. the Performance Line is noticable. The tweeters sounded cleaner and (I think) contribute to a much wider soundstage. Switching between the Titans and the Mini Monitors produced a noticable jump in sound. The Titans are good in their own respect but the Mini Monitors are simply better.
I am poor and the Monitor 5s were more money than I wanted to spend but I simply felt that they sounded better than the Atoms, Titans, and Mini-Monitors. I intend to keep these speakers for a long time so I let myself spend a little more and picked the Monitor 5s over the Mini Monitors. They sound very similar but the 5s just had something extra over the Minis.
Now that I have the Monitor 5s in my own home and playing on my own receiver I feel good about the decision to buy them. I had to order shielded versions since they weren't in stock and during my wait I built some stands which turned out pretty nice. The Monitor 5s amaze me with the ease at which they image. They certainly image better than any speaker I've owned and sometimes I have to check to see if the center channel speaker is playing. The width and depth of the soundstage is much better than I'm used to hearing. Otherwise, my impression of these speakers is that they are very neutral. They don't draw attention to themselves at all which I guess is good but seems weird. I don't find myself thinking "wow, listen how good my speaker sounds" but I simply hear the music for what it is. I find myself analysing the quality of the recording and forget about the speaker. This is strange because I used be more happy with the recordings and more distracted by my speakers. It seems strange that I can't find anything that I can say is great about these 5s but, given much though, I can't say anything bad about them either. To my untrained ear they do everything I want them to and do nothing that I'm not expecting them to do. I guess as far as speakers go that turns out to be a pretty good endorsement.
The CC-370 gives a somewhat similar impression. The CC-370 is actually more expensive than one Monitor 5 and part of me wants it to sound better than one Monitor 5. It doesn't, but it doesn't sound worse either. The 370 just does what it should and nothing really jumps out at me to say about it. It (to me) is very neutral and pretty natural sounding. My biggest complaint about the 370 is the shape of the cabinet. I have to set it on top of my TV and certainly don't need it naturally angling up. I used a rubber wedge under the back to angle it down at my listening position. It seems that designers should make centers such that in one position it angles up slightly (for under TV use) and when flipped upside down it angles down slightly (for on top of TV use).
To answer the question that I orginally posed - I feel the Onkyo TX-SR601 (85 watts) does have enough power to drive these speakers. The Monitor 5s get quite loud before I feel like the amp is running out of headroom and compressing the dynamic range (I think this is what is happening?). At a listening volume that would still allow a conversation in the room they sound good. If I turn it up more I feel like they sound better. Only at extremely loud levels do I feel like the amp is running out but that the speakers could still handle more. The Onkyo does fine with these speakers.
