Interesting discussion! :-)
I can't add any info about alternative speaker choices (given my biases :-) , not that I can think of anything besides some of the speakers already mentioned which would approach close to full range or full range type performance with a 20W SET amp), BUT I can add some thoughts about using subs with VSMs . . .
Many are right, Bobby would not like using the VSMs without the BAM and subs. It can be done though - from what I have just read of the Funk subs on their site and some reviews, given its DSP and crossover point adjust-ability - integration should not be a problem (especially with two subs vs one in my experience). I would certainly give it a try.
Though with the BAM, I would like to point out you can get a very good sub-woofer - VSM system. It has been done.... I have a long time local customer who has owned Merlin VSMs (updated) for many years (With Joule-Electra preamp and a old pair of Joule OTLs). His system is set up in a huge space (the home is pretty much a open barn like space and not a small one - the volume is quite large). Years ago (still in use today with some minor changes) we set up this sub set-up: two large (physcialy twice plus the size of the Funk 18.0's mentioned in this thread) Infra-Sonic (I think that is the name, the company is long gone) passive subs powered by a large 600W/ch Crown Macro ref amp, with Bryston active stereo sub woofer crossover used to set the low pass (top freq roll-off) for the subs.
One output came from the preamp, to the BAM and then to the OTLs. The other output from the preamp went to the Bryston and then to the Crown amp. I did the fine tuning of the level and crossover point by ear (this was around 2000 - before such cheap handy DSP stuff and measurement tools were available!) I wound up running the subs up to around 40Hz. Yes, that meant a fair amount of overlap between the VSM/BAM and the subs in the 30 to low 40s range, but with things phased right the results were/are downright majestic. Whether a big full scale Orchestral work or something like FourPlay, this setup had/has wonderful impact and scale. Jerry's set-up is probably the only VSM based system I've heard that had that big a sense of scale (I'm sure the large size of the room/space has something to do with that).
BTW, in a larger room with stereo subs, I would also try pulling the VSM's wider apart (more so that the approx 6ft Bobby usually recommended) with a bit more toe in. The added fullness/weight added by the subs will help fill things in allowing the speakers to work better further apart - probably give a bigger sense a scale/stage.
Hopefully this tale provides some fuel for thought. I'd hate to see anyone sell their (Black Magic) VSM! :-) - Rich
