how do you select a center channel to match when the company only makes monitor speakers?

I have had dealers recommend using a single speaker from same speaker line. I think that makes the most sense as well. Obviously it won't be a traditional center channel speaker, but the voice matching would be, and that is what you're after. I eventually will be in the market to replace my speakers and have decided that I may be doing that as well.  I have a dual (2 channel/HT ) system, and I want to buy speakers for sound quality in 2 Channel, as it appears you are doing.

I would try to see if you can buy a single Harbeth.  Maybe a smaller model within the same line...... It's unlikely another brand will be voiced similarly. ....

I would try to see if you can buy a single Harbeth.  Maybe a smaller model within the same line...... It's unlikely another brand will be voiced similarly. ....

Agreed

If your HT room will have an AT screen, then a third Harbeth of the same model will be your best choice.  Otherwise, go with the best sounding speaker that will fit your space and be as timbre matched as possible.

Bill