I never thought I would say this, but I would suggest you listen to the Classe CAM-350 Monoblocks. New they are $7k, but I'm sure with either dealer discounting or perhaps a demo/used pair would fit your budget.
They are the perfect size, not too big. I just recently heard them with a Classe Preamp (not sure which model), and the Musical Fidelity Nu-vista 3D CD Player. They were driving a pair of Audio Physic Virgo III's.
They were quite dynamic. There was just a tad bit of smoothness/warmth which could be attributed from the Musical Fidelity CD player, but nonetheless I really liked the sound. There was nothing dry or unenvolving about the setup - extremely musical (I'm sure that's why they made the Stereophile's Class A recommended components list.) I have been also considering to buy them.
The CAM-350 monoblocks sound nothing like Classe's older stereo amplifiers which were too bland for my taste.
I've used a pair of Pass Aleph 3's (obtainable for around $1000 each, with patience) very successfully as monoblocks, paralleling both input and output, as per Nelson Pass's recommendation. My only knock on these amps is that they take an hour or so to reach their top performance. But their top is pretty high, if you like solid state at all, IMHO. I think you could do a lot worse.
You should add the Bryston 7B-ST monoblocks to your short list. They are of reasonable size, offer a combination of excellent power and sound quality (rated "Class A" by Stereophile mag), and have a 20-year transferrable warranty backed by probably the best service in the high-end industry. A new pair sells for $5000, and can often be bought used for around $3000-3500.
With your BAT preamp, consider BAT VK60's mono. Used for around 5k. Not exactly small...but great match with the wadia, 3i and speakers...
Have you considered the BAT VK-500? It's a single unit with two monoblocks in the enclosure. Two power cords, two power switches...
I would add Clayton M100 monoblocks to your audition list. Output is rated at 100 watts / ch. class-A. It has both RCA and XLR inputs, and its relatively small size would fit your living room as well. Check out www.claytonaudio.com for more info.
I second the opinion on the Classe CAM-350s, my present amps. But if your speakers don't need that much power, before the Classes I had Pass Aleph 2s, and they were wonderful. There is usually a pair or two used on Audiogon.
Not sure if you want to keep with SS amps or not, but bear in mind that your speakers were likely voiced w/ tubes. Pat McGinty seems to like the 6550-based 100 wpc Music Reference RM-200 a lot (has his own, demoed the Nightingales at CES w/ them a couple of years ago, plugs it at the Meadowlark web site). It doesn't fit your bill as it's stereo but gives you an indication of your speakers' designer's thinking. Also remember that all Meadowlarks are designed to be tube- and modest power-friendly. Some of the above recommendations, while great amps, are overkill for your birds, which should sing sweetly around 100 wpc, assuming high quality power.
There seems to be some degree of consensus among Heron owners at Audio Asylum that the Herons prefer EL-34 based amps. The whole-hog answer to this would be a pair of the new Cary V-12s (though most of these are stereo amps, Cary does wire them in mono as well). 100 watts each in triode mode, 12 EL-34s per side. Unfortunately, they are not at all small and go for $8K (per pair) new, though, so probably not the best answer - just the best LOOKING answer.
Another option is the VTL MB-125 monos. 4 EL-34s, 55 watts triode, 100 tetrode, compact; only drawback is no balanced inputs. VTL's 6550-based MB-185 Signatures have balanced inputs and more power (105 triode, 165 tetrode) but are definitely bigger (std 19" width, 9" high).
I've gotta second the VK-60 suggestion as well given the rest of your components. This is another amp that Meadowlark has used at CES and gotten (claimed to, at least!) great results with their speakers.
Check out Pass Aleph 2 monos. 100 watts single ended. I use them with a set of Meadowlark Kestrels and I think they are a fantastic match. BAT VK60s are very nice, but they are huge and will heat a small house. There is a set of Aleph 2s on this site for sale at a very reasonable price.
I am intersted in hering the Plinius Class A stuff.Posts on audioreview.com are ga ga.These Bel Canto digital amps are getting the rave too.Youmay not need to spend that whole wad and get something decent.Oh yeah one guy who owns a shop say's the big McCormack is the best amp out there bar none and I think it fits your price tag.Hell with that budget I'd dump the Herrons and go deeper in theri line or give yourself some options with a new amp and start auditioning speakers not that the Herrons are anything to not like.But that's a big amp budget considering what your going to end up hooking 'em up to.Budget concious?Check out the Monarchy class A amps.Like Rogue evrybody thrwos in word "value" when they talk about them.
Look into the Monarchy Audios. There are 3 or 4 models that are all pysically very small. I had a pair of SM-70's running in fully balanced mode and I couldn't believe how good they were. I paid $700 for the pair used in perfect condition. For more power and improved overall performance, there is the SM-70 Pro, then the 100 deluxe, then the awesome 160 deluxe. All are a bargain, and Monarchy's owner, CC Poon will give a discount if you buy direct. See the website at www.monarchyaudio.com.
BTW, I sold the SM-70's to a tube fan and he loves them. This is one of the most tube-like SS amps he's ever heard.
Yep, another vote for BAT. VK60monos - around 4K used, upgrade from VK3i to VK5i - it's gonna be a killer setup
Don't forget the Aronov 9100 tubed monoblocks. They sell for $ 600/pair new, but you can get them used for $ 3000 or less. This are great with my BAT VK5 and Sonus Faber speakers. Output is ~ 120 watts per side with KT88 tubes. I got mine second hand (traded a pair of Bryston 7BST's for them!), and have done some modifications to them, including Cards binding posts, WBT topline RCA jacks, and extensive chassis damping with EAR Isodamp. Will definitely hang on to them until I can afford CJ Premier 8's or a pair of BAT VK75SE monos, but would not trade them for anything less than that!
Thanks to all of you for taking the time to respond! Lots of information here to digest and as I proceed, will keep you informed.