The 9444A and 9440 are well thought of. The 9440 typically commands high prices on the used market, the 9444A is much more reasonable.

The 1590, 94, and 93 are okay, with some caveats. The 90 isn't as well suited to HiFi as the other two, I've been told. It's a 200 watt mono amp...... actually they're all mono. The A versions are "positve ground" (at least the 1594A is)...... which isn't something I understand since they're not automotive amps. The A's are a hard sell.

1590A, B, C 200 watts
1594A, B, C 100 watts
1593A, B, C 50 watts

I've actually got a pair of 1594A's and I think they sound fine, but I'm no critical listener, either. I used to have a 1590A, but after trying several times to sell it, or even give it away, I finally gave it to Habitat for Humanity, and never saw it again..... I'm guessing it's either still in their warehouse, or they scrapped it.