I had a PT6 for some time. Change out the cable before you go anywhere else. That makes a big difference, for sure.
I recently upgraded for a Moerch DP6. Phew - no comparison there in performance. Amazing arem, that Moerch, but I did have some mounting issues to contend with.
The PT6 has a rather large mounting hole ... the DP6 (I must like the #6) rather small. I had to route out a flange in the plinth, top and bottom, then use 2 steel washers to mount the Moerch. This gave me a little play in the overhang distance, which is quite similar to the AQ, give or take a few MM. The Moerch PT4 has the same mount as the DP6, I believe.
I was unable to find another higher quality arm that was closer to the mounting distance than the Moerch. Perhaps the Hadcock, but then there would have been cartridge compliance issues to contend with (as there are with all unipivots).