Speakers...
Hornshoppe are those very little very nice back horn loaded full range drivers, Fostex right?
I can bet your problem is the Whizzer...
I used to have a kinda Bazzilla speaker with DX3Lowthers on open bafle, I had to really fight ot get the SSSing down.
First point: silver cables give cleaner highs.
Second point. Add a super-tweeter, I started with a Fostex FT17H and then upgraded to a Beyma CP21-f
I have the Martin TL boxes with Fostex FE 207E drivers on a second system and its pretty nice, I got those to get better bass than I was getting with the the Lowthers, transparency is better with lowthers though.
I think you have a great system, I dont mean to be rude but I think its time to upgrade your speakers, I got Cabbase Loudspeakers after a lot of fiddling around with Full range drivers and they beat every Fullranger I heard in any aspect, more transparent more dynamic more coherent and of course better bass and better highs.
They say lowthers have a lot of bite, my Cabasse have more bite than my lowthers, I had to tame them good and they are sooo sweet now!!
PS- Not connected to Cabasse....
All the Best