Warmest sounding Green Mountain speaker?

I have a pair of Continuum 1.5s from around the year 2000 and I had the privilege to hear several other GMA models, as Roy Johnson used to let me hang around his shop in Old Colorado City and help burn in new speakers while I was trying to decide if I wanted any of his speakers and then later while I was waiting for mine to be built.
I also am familiar with and like the new Vandersteens. I just heard the new model threes (I think that's what they were) this weekend and they were terrific. The Quattro Woods I also like.
I'm not really sure what you mean by "warm", though.
I can tell you I love the Continuums for their ability to play loudly (and still sound good) and their ultra-modern looks.
The smaller GMAs, I think they're called Callistos, are also very cool but I don't recall them sounding, well, as big.
Those Vandersteen threes I heard this weekend did sound kind of mellow; maybe that's what you mean. Smooth and easy to listen to. The GMAs do not have that quality, at least not as much. But I think they make up for it in other ways, particularly in detail and realism. Listening to drums through GMAs is always surprisingly realistic and makes you wonder why quick sonic transients like that are so shortchanged through other speakers. I think this makes the GMAs ideal for rock and pop, maybe less for classical or bluegrass.
I'm sure I didn't help much, but I think if you get a chance to hear the GMAs you'll be able to tell right away whether or not they're for you.

Personally I think the GMA speakers work well with all types of music. But that transient speed is what makes them shine with acoustic music like bluegrass.

Shakey

I havent heard the bigger GMAs but the bookshelf models I have heard are clearly flawed in the bass region IMO. The mid-upper bass which gives an acoustic instruments its woodiness character and to some extent the body was lacking seriously IMO.

Agree. The lack in the mid upper bass is due to the tiny cabinet volume of the bookshelf models. Anybody know how many litres Rio uses?

Apart from that, the driver they use is an aurasound woofer. For the price of Rio, you would expect accuton or scanspeak revelator etc.
Not a $20 woofer!

I've had the Green Mountain Audio Callistos in my system for the past ten years and have not had the desire to upgrade speakers since that time.  Before that time I was always looking to upgrade my speakers.  If I ever do upgrade it will be to another newer Green Mountain Audio speaker.  I've listened to four of their models and they all have a very similar sound signature from the upper bass on upward.  Most of the models use different drivers but I believe the sound is so similar due to the unique first order crossover and dead quiet cabinet construction.
The speakers are very efficient, easy to drive and play very loudly.  Transparency, soundstaging (especially depth), microdynamics, inner detail, and reproduction of the human voice are extremely well done and I really haven't heard better in those areas from most other speakers I've listened to. Six moons gave these speakers a phenomenal review ten years ago.  I've had several members over my house from an audio club I belong to and all agree they are first rate speakers and cannot believe such sound quality coming from relatively small monitors.
I do agree that the monitors do not have a lot of deep bass however the bass is very tight and controlled.  I'm using a Rel Storm III sub which integrates seamlessly with the Callistos.  I'm using a hybrid integrated amplifier so I agree having some tubes in the playback chain is worthwhile.  I have not compared them to the Vandersteens.
Just my opinion.

Apart from that, the driver they use is an aurasound woofer. For the price of Rio, you would expect accuton or scanspeak revelator etc.
Not a $20 woofer!

kenjit, it's not about how much a woofer costs w.r.t. the total cost of the speaker that dictates whether or not it gets used. It's the specs & the freq response that it far more important as that tells the speaker designer how it will integrate with the tweeter & midrange. So, if a $20 woofer has the correct attributes over a $200 Accuton woofer, then, the $20 woofer will be used. I'm sure that Accuton builds good woofers but for this particular Green Mtn Audio speaker the Aurasound woofer was a better fit. I know that Roy is always looking for the best drivers & I understand that the choices are limited to independent OEMs. So, that also puts a big constraint (unless the OEM wants to order a very large batch of Accuton drivers as a minimum order from the manuf which many small OEMs cannot afford).  
I've heard a few Accuton-based speakers incl a stand-mounted Tidal - I cannot say that i was impressed with the sound. The Green Mtn Audio speakers sounded way better to me.