Bi amping a pair of B&K ST-140's

I suspect that wouldn't work out well. The impedance of the speaker is spec'd as 8 ohms nominal, 4 ohms minimum. I would suspect that the impedance is in the lower part of that range in the bass and/or mid-bass regions, where lots of energy is typically required. As you'll see in these measurements the ST-140 has significant issues dealing with 4 ohm impedances.

Also, the ST-140's input impedance is spec'd at 24.3K. More likely than not the two output jacks provided by your preamp for each channel are driven by the same output stage, with the two jacks simply jumpered together just inside the rear panel (as opposed to each jack being driven by a separate output stage). If so, and if you were to drive two amplifier input channels from the two output jacks the preamp provides for each channel, the preamp's output stage would see a load impedance of 24.3/2 = about 12K. That will be too low a value for some preamps to drive with optimal sonic results, particularly if the preamp is tube-based.

Regards,
-- Al

IMO, a biamped pair of ST140's isn't close to a pair of M200's (I have both). If you don't have the patience to wait for a pair of M200's, I might look for a Parasound HCA2200 (I've also had one of those).

Do you have the older or the newer m-200's? I actually found a pair of m-200's but they are the older model with the captive power cord and the rack handles. Are there any other significant differences?

I have the older ones, plus I have one of the newer ones that I use for a center SPL. The old ones are one of the best values around.

The difference is mostly packaging afaik. I also had mine nodded at musical concepts.

The guy that has them is asking $850 for the pair. Is that way out of the ballpark in your opinion?I really want them and know I cannot go wrong buying them, but I also don't want to overpay.
Thanks

Also looking at a nice Ex442 sonata. I'm thinking that would also be plenty of power for the B&W CDM 7NT's

850 is high. I've seen them as low as ~450 in rough cosmetic shape to ~700 in good shape.

I'm not familiar with the ex442.

I'm in agreement with all of the above.
The older, original lower powered 70 Watt ST 140's were a bit better into lower impedances than the later 105 Watt ST 140s.
Having had both the ST 140 and M200's in my system, I can verify that they are indeed very different amps.
Do keep in mind that these amps, due to age might need some maintenance; such as new caps.