Is there a point of diminished returns with amps and Harbeth 30.1s?

I know you are asking about amps, but IMO, contrary to Alan Shaw's opinion, speaker cables make a big difference.  I've owned the M30s, SHL5s and P3s and I've found the right speaker cables to improve the sonics significantly.  I don't know what you're using now, but if you have to move the speakers often, I would see if the Cable Company has any more Audience AU24 show demos at 1/2 price.  Excellent sound and very easy to work with.  I also love Purist, but they are not the cables to be moving around on a regular basis.  Not that you can't, but they are kind of bulky compared to Audience. 

@dhcod - I absolutely hear what your are saying, but after trying some better cables with several Harbeth speakers and hearing the dramatic results, I think you are closing yourself off from a possible big upgrade. Your system is very nice and I’m sure well-tuned to your tastes. IMO, you should at least borrow a set of cables from the Cable Company and try them. This way you will know if the Ohno is the bottleneck. No other way. I think you might try the Purist Poseidons or the AU24s, as I have heard them both and they sound amazing with Harbeths. I have had systems where 10 gauge Beldens worked fine,, but others in which they left a lot to be desired. So that’s my opinion and the rest is up to you. Who knows, you may luck out and say the Ohnos are just as good and move on. Or you may find that the new cables brought sonic upgrades beyond what you thought.  

@dhcod - Just remember that it doesn’t matter what anyone else hears, claims to hear or claims to tell you what you should hear. All that matters is what you hear in your home, in your system. Then you can relax and listen to beautiful music while others are too fired up trying to push their views onto you. I was a conservatory-trained musician in my youth and one thing I learned is not to assume someone else cannot hear something that you can’t.