VALUE!!! While my HCA is no longer my primary amplifier, it's now powering my outdoor system. Decoupled the transformer from the chassis, Black Gate caps, and a beefy DIY shielded AC chord, made a considerable improvement. I wouldn't hesitate to suggest a used one and have the full RAM mods done.
I didn't experience any of the high or mid range issues mentioned above and I went from a tube preamp to solid state/battery. Upgrades in digital playback, phono cartridge, and speaker system, were clearly noticible using the HCA. At first the bass seemed only slightly thin until I compared it to a couple of amps that are famous for their bass reproduction and upgraded my preamp. I preferred the more precise rendition of the HCA, and I'm not calling it tight, rather much more accurate in timbre. While the other two had more of that flabby bass that many seem to enjoy, the HCA has the ability to start the note quicker than the others, IMO.