Harbeth M30.1 vs B&W CM10 s2

My current gear consists of B&W CM10, Parasound A21 and Cambridge Audio Azur 851D (preamp and DAC). My taste in music -- jazz, blues, light rock (e.g. John Mayer). No interest in pop music, rock, metal, rap, etc. I am not really dissatisfied with my current system per se, but there are times when I find the speakers to be a bit on the bright side and lacking warmth. I am also planning to add a subwoofer (or two) in the near future, so musical sub recommendations are also welcome.

I have an opportunity to buy a used pair of Harbeth M30.1. I have heard great things about Harbeth. The problem is that the seller lives about 2 hours away from me. So before I make the trip, I want to get some feedback from folks who own the Harbeths, or better yet replaced B&Ws with Harbeths.

If one’s taste in music leans toward jazz (classical and contemporary), vocals (Diana Krall, Patricia Barber, Shirley Horn, etc), blues, and light rock, do you think Harbeths will be a step up in sound quality compared to the CM10s? I am looking for more transparent, detailed sound but not at the expense of losing the bottom end/oomph.

The speakers will be placed in the media room. Roughly 15 x 20, 10 ft ceilings. No windows.
I have Harbeth P3ESRs in my study and by all accounts the sound of Harbeth speakers is very similar across the audio range. I think they are glorious and in particular not at all fatiguing or over bright. Thanks in part to the very special cone material they are also highly transparent and with a clearly spacious sound not at all dissimilar to the Quad electrostats in my living room. The M30.1 is also the model that is probably precisely right for the size of your listening room.

I feel that I may have seen a Harbeth 30.2 soon to be available...Just saying! I enjoy my P3 esr's very much, especially for smaller scale, acoustic, and vocal stuff. Great advice from willemj above with regard to choosing the right size speaker for your room. I would have guessed the SHL5 would work in a 15' X 20' with 10' ceilings, but I may be wrong.

I doubt that you would go wrong with the Harbeths. I have the smaller P3’s in my 20x15 listening room and I like them better than many other speakers that I have owned. If you want to add a sub the J.L.Audio goes perfect with the Harbeth. BTW, I always found B&W to be a bright speaker!
The M30.2 is a special anniversary edition with a different (I think ugly, but that is a matter of taste) veneer. It does not replace the M30.1, so the numbering is a bit confusing, I think.
If you ever consider subwoofers (I like them), get (at least) two smaller ones instead of one big sub for a smoother response. And use room eq like the DSpeaker Antimode 8033, to tame room modes. See here for a first introduction: http://www.acousticfrontiers.com/20101029using-multiple-subwoofers-to-improve-bass-the-welti-devanti...
For your taste in music the Harbeth are a fantastic choice. They have one on the world's best tweeters (Excel Millenium) and Harbeth mids are to die for. Not the last word in bass but miles better than the badly engineered B&W.
I want to thank everyone for the wonderful advice.

So today I went to the seller’s house for an audition. As expected, the sound was very transparent and airy. I could tell that the mid’s were miles better than the B&Ws. No contest there.

However, his music room was relatively small - I think maybe 10 x 12 with 12 foot ceilings. The couch was probably no more than 6 feet away from the speaker. The speakers were placed only 6 feet apart. I don’t know if it was the room or what but the speakers didn’t have the full sound that I was hoping for. And I don’t mean loud. I was expecting that they would fill the small ’ish’ room and disappear, but they didn’t.

A few months ago I had visited a dealer to listen to the Sonus Faber Olympica 1s. I absolutely loved the way they created a wall of music and disappeared completely. The base was astonishing for such small speakers. Somehow, I didn’t get the same feeling with the Harbeths. And yes, I am cognizant of the fact that the dealer might have been using better gear and acoustic treatments.

I am very well aware that it might have been the seller’s setup, but somehow I am not convinced that the M30.1 are enough given the dimensions of my media room. The seller is not too keen on bringing them to my house before I buy them, so that’s probably not an option. Also, no Harbeth dealers where I am. I just wonder if the SHL5s would be a better fit for me. Maybe wait and see if a pair of SHL5s shows up at agon?
Given what given what you have said you are looking for you have described the sound of the Harbeth SHL5+’s. I am happy owner of the SHL5+’s but I have never heard the B&W CM10’s and can not compare the sound of the two. There are a few pairs of the SHL’s for sale on AGON right now for good prices.

My only caution would be that you probably can’t listen to them before you buy unless they are near you. For me, I would not buy any speaker I have not heard personally. Any opinions you get are just that and are based on the listeners priorities and experience with the speaker they know. I have always believed that the speaker is the most important component in a system and you need to start there. Have you discussed this with your audio dealer? They may have some good advice for you. Good Luck!
The M30.1s sound quite different from the SHL5+. The M30.1s are capable of sounding big in a larger room fed with good power. Nevertheless, the SHL5+ will have a larger and more enveloping sound than the M30.1 apart from deeper and fuller bass.

The M30.1 has the small studio house sound which is great for vocals and small musical ensembles playing some jazz. However, it doesn’t sound as airy or open as the Compact 7ES3 and SHL5+ which are more of an all-rounder in my view. Personally I prefer the SHL5+ more than the M30.1 but that’s entirely based on my listening taste and personal preference. As always, it is best if you can listen and decide for yourself.
For the moment, I have decided not to get the M30.1. As others have mentioned, the SHL5+ might be a better match for what I am looking for. Unfortunately, there's no way to audition at the moment. AFAIK, there are no Harbeth dealers near me, and I'm leery of buying before listening.

One thing I'm also realizing is that I prefer full range (3 way) over the stand-mounted monitors. I like the intimacy of the small speakers but they might not be a good fit for the current environment. Perhaps, when I set up a smaller system in the study, I can look at the Harbeths again. I really liked their overall house sound.

I guess I'll stick with the B&Ws for the time being and save up enough $$$ to buy the Sonus Faber Olympica II or III (used), which I auditioned last year and totally fell in love with.