Mark, I'm not a big believer in the importance of cables, but the question is which cables are you using? I use an old Audioquest model, Crystal 2. It was a step up from the Indigo or Type 6, which I think you still see selling some places. It was $10 per foot retail, the same price as the Kimber 8tc at the time. I thought the Kimber was bright, an MIT cable I tried dull, and the AQ just right, but I don't trust my observations of wires.
It is more likely that you are hearing reflections off ceiling, walls, windows or hard furniture. Try experimenting with toe-in. Use a mirror to find the first reflection points off ceiling and walls and stick some soft carpet material at those spots. If you have windows, pull the drapes. Put blankets over hard furniture. Remove glass topped tables. Short of all of that, to analyze if it is the room, toe them in and listen near field to eliminate the effect of the room. If it sounds the same to you, then it's the speakers or something else in your system.
The Harbeth's tweeter has very wide dispersion, which makes the speaker sound a little toppy in live rooms. Mine sound fine in my larger room, far away from walls, with no suspended ceiling.
Glad to see you're making progress. If you are using metal stands, did you fill them? Soundbytes are good for that purpose, or unscented kitty litter from the supermarket. Just as an experiment, try uncoupling the speakers from the stand (I'm guessing you're using Bluetak or something like that), and putting a towel or some paper napkins between the speaker and the top of the stand. Sound different?
