Monoblocked Bernings ZH-270s?

Yes, the zh70 can be "strapped" for mono operation at 140 wp monobloc. I do not own them, but have a good friend that does own them.

The monoblocked Bernings with their 140 wpc and high current delivery will drive even the toughest loads. I heard of at least two people that are using them on their MBL 101's with amazing results. However, even with easy to drive speakers there are significant benefits to using these amps as monos. They sound much more effortless with better dynamics, improved overall clarity, even purer midrange and richer and more natural harmonics. In my system these little beasts bettered two different amps that cost well over $20K! If you're buying a pair, make sure they are of the same vintage as there are differences between different production runs and you definitely would want them as a matched pair.

Yes, I have a pair of 270's running as monoblocks. Markxiii is right, be sure to buy two from the same time period, early versions of the 270 had a different input impedance than later versions, and the 'transformers' in the earlier versions were physically larger than those in the later versions. Having said that, I got amps from two different periods, but fortunately David was kind enough to update the older one to current status, don't know if he has the time or inclination to do that anymore, so make sure they are from the same time period.
Markxiii is also right about the sound of monoblocked Bernings. In fact, if I had the money right now I'd probably buy a third 270 and run it in stereo for the tweeter on my Merlins. Overkill, maybe, but sure would like to hear it.