I have not heard the Harbeth but have heard the IB1s extensively. It depends on your musical and sonic tastes. I found the IB1s to be too "punchy" for my tastes. I felt the bass was a bit pushed out or forced, which the higher end MB2s corrected. But you may consider that simply as dynamic to your tastes. With that said, I do like the IB1s and would be happy with them if I had ended up with them.
PMC IB1 Vs. Harbeth M40
I'd appreciate your thoughts on how these two speakers compare with each other sonically. I know the PMC speaker is much more expensive than the Harbeth speaker, but both are large monitors and their companies' flagship speakers and both are used in professional settings. Thanks