Thanks Alex -
I agree - the tinkering is a lot of fun. I decided to strike while the iron was hot so I've also popped in a new pot (not stepped), power supply choke and film output caps in the last few days. I also bypassed the last PS cap with a small 2.2uF film cap. All challenging & a really great experience for me in terms of thinking outside of the manual a little bit.
To be honest I never really had any problem at all with the stock pot, but I do feel the better pot I have (TKD) is somehow a bit cleaner and less rough. The TKD feels incredibly silky so the user experience is really nice, that's for certain. Quite ridiculous when you think about the price in relation to the cost of the amp though of course. I also padded the pot with the resistors, as you did a while ago, which is GREAT as I have much more usable range on the dial now.
Crack is addictive.
Definitely post an update if you go ahead with the stepped attenuator!