hi Prof, boy it has been an interesting six weeks since i first got them. first week or so, they were not very good. they have improved enough that i prefer the sound of them over the 2.7's. for a point of reference i would assign the 2.7's a sound quality of 8. at first the 3.7's were about a six as they were bright and one dimensional. now they are at 8.5 and improving as they were essentially new speakers, and from all that i have read, they need 200 plus hours to really start sounding their best.
they seem to be more extended, accurate, and less congested. that said, i could live happily with the 2.7's. and i do like the more compact size and looks better on them as well. my girlfriend likes the "warmer/sweeter" sound of them but i think she likes the bit of mid bass bloom that the bigger ones do not seem to have. overall two awesome speakers and you are right, in that whoever gets my 2.7's, is going to be very lucky.
the sub is an REL S/5 and i really like what it adds. seemed to mate well after playing with room placement and the settings. Paul at PS Audio is who turned me on to them. They are his faves as well. they are very easy to hook up, just run their cable from the outputs of the amp right to the REL using their special connector.