how do maggies sound with b&k st-140 amps?

For a while, I drove a pair of MGIIIs with an ST140 in a room about your size. If you listen at lower to medium volume levels, you should be fine. Another option would be to look at SMGAs or MMGs. I am putting a system together right now composed of Counterpoint 7.1 tube pre>B&K ST 140>Magnepan MMG It will be going into my basement.

There are many models to choose from under $1000.00.
I think any of the ones you have mentioned will work just fine with your amp and room size. I doubt you will feel the need to bi amp those models.Some of which cannot be bi amped without some modifications. Try out some MMGs ($550.00) and a Panny XR 25/45 ($300.00) both can be returned so you have nothing to lose. The combo will put you at roughly $900.00 with shipping and you get a decent tuner as well! This will save space and give you some seriously sweet sound for little money. I guarantee you will be scratching your head trying to figure out how something so inexpensive can sound so good.
Also with the left over money you can pick up a Adire Rava($400.00) sealed sub and be in heaven! All you need to add is a cd/dvd player as a transport. That will leave $300 for cds,cables ..etc.
Happy Hunting!

But the right channel blew up, due to the wife's vacuum knocking the wires off the back, and so I had it re-built but while I waited I found a T-hold and so now I have rebuilt 442 gathering dust.

I would go for a used 442, or used T-hold if you can swing it. Or a Krell KST 100 should be under 1000K, the 442's can be found for under 500, and from there just keep your eyes open, I don't recommend tubes, in any part of the chain with Maggies, the bass and highs are already a tad on the weak side and the majority of the tube equipment in the price range your looking at just doesn't do it. There are tubes that match nicely but not at under several Kilobucks used.

If all you can swing is the 140 go for it.

loon

Highs a little on the weakside?? HuH!!
Loonton I take it you haven't heard Maggies with the True Ribbon tweeters! I am talking 40 KHz extention..just how high do you need it? Bass isn't thumping on Maggies but it is very articulate and well defined.

Gmood1...True, Maggies are not known for "thumping" bass, but, I just modified my MG1.6 using a 10AWG air coil inductor, and I think that this may be the solution to that problem.

One of the advantages of being 66 years old is that you don't need to spend a lot of money on 40KHz tweeters! I like the QR tweeter fine.

I hear ya Eldartford ...I have mine padded down with 2 ohm resistors.It would be too much of a good thing for me as well LOL!!! I like the extention but it must be kept under control. I noticed things really opened up after bypassing the fuse and metallic sounding steal attenuator. Also replaced the stock resistors.Transparency in spades now.
I listened to Medeski Martin and Wood the other night I could actually zero in on a conversation going on in the background...while the band played.Never even heard this before on the this recording..next step maybe some new inductors and other crossover parts.