Audio Research versus McIntosh tube amps: anyone experience or compare both?

Ever thought about biamping. Maybe see if pairing your existing solid state monos and a 275 for McIntosh or better from audio research since you have their preamp for the mid range and tweeters. You have a nice size room and maybe it's underpowered. Lots of windows which you know about and maybe it's fine. I am in love with your rack.

I'm using a McIntosh MC 901 and find it works out really well . I'm exploring replacing all of the smaller tubes with NOS telefunkens. Replaced a few of the small tubes with good results and I need to complete the transition. I like the independent control of the drivers and I didn't want to deal with complexities of crossover components so that's why I got the 901. 

I'd be concerned about maintenance on an audio research product longer-term. Would recommend buying from a dealer if used.  McIntosh is reliable and built like a tank and sounds really good and is not midfi.  Would encourage you to get better tubes than what it comes with.