I have prevously read that the HCA-2 might have a difficult time with low impedance speakers.
The following is a direct quote from the PS Audio forum in response to a HCA-2 owner who happens to be the Jason, the President of our ML Club. I'll include a link below, although you might have to create a user name to get into the forum:
Quoted directely from Paul McGowan, owner of PS Audio:
"Thanks for the kind words. And, yes, the new cables just chew up anything in their path. Thanks for this note and we look forward to your extended review.
The HCA-2 just shuts off - and you think it is unrelated to the musical content? I mean, if you play something - it apparently doesn't matter what the level is or the particular point in the track?
I've not heard of this malady. The HCA-2 was never great on low impedance loudspeakers and the ML's can dip. But you suggest you've been playing them for a while. The two possib ilities are that the speaker's transformer has developed some trouble and the HCA-2 is simply responding properly, or the HCA-2 has a problem.
I suggest running the amplifier at another member's house with ML's. If you have the same problem, t's the amp and we better have a look at it for you."
End Quote
Now with that being said, I believe Jason's problem was minor and taken care of easily (please read all of the thread). I'm not trying to slam the HCA-2, because I've actaully been considering one myself. There's been a lot of used ones on Ebay and Audiogon for around $700.
But Paul's comment made me second guess my desire to get one. If you can you might want to get one try it out and worse comes to worse put it up for sale. The HCA-2's price has been pretty stable at $700 for some time and going fast at that price. So you decide you don't like it, sell it for $600 or $650, undercutting what's out there. I think your risk is limited to roughly $150-$200.
Research as much as you can. Paul McGowan personally responds to questions on PS Audio website forum.
Whatever you decide, let us know, and as always "Trust your ears".