IMHO. HK signature 1.5 , AP 2500. Certainly I’m no expert, but after working in a music store and listening for a couple of decades. I’ve heard my share of good and bad. YMMV.
Matti Otala’s design influence spread from the superb HK Citation XX to harman kardon’s early 80’s amps. Powerful and clean. Very capable of driving demanding speakers with aplomb, and reasonably priced.
When restored utilizing the accepted recipe, caps, L pads, possibly tweeters and/or woofer surrounds. They deliver excellent results. One of the most satisfying restoration projects I’ve completed.
When I was collecting Zenith transoceanic’s many years ago. Soaking the detectable antenna rubber cups in a bowl of armorall for a couple of days restored the playability of the rubber.
The HK-230 was my first tube amp and guilty of exposing me to that wonderful sound. I think the 6bq5 is at least partially responsible, along with excellent circuit design. Your patients and effort will be rewarded.