Pass First Watt models ... confused

I'm curious about the First Watt products. I'm a very happy owner of a Pass x250.5 AB amp but interested in experiencing full class A. No plans to sell my less than 1 year old x250.5, and I'm not rich so I won't be sinking cash into the exorbitant prices of a new XA series. A used Aleph is a possibility, but those are getting fairly old and I wonder about maintenance issues.

Therefore I am looking at the reasonably-priced First Watt line from Nelson. But I'm quite confused by all the different models. Can anyone help clarify this puzzle for me? Thanks.
You're right about the limitations and the need to have appropriate
speakers to get the most from these amplifiers. The 6 Moons articles-
reviews spell this out very clearly. Apparently with the proper speaker
match these amplifiers are quite exceptional. No surprise actually, great
designer, class A, very simple circuit with fewer parts (but good quality) =
good sound.
"A used Aleph is a possibility, but those are getting fairly old and I wonder about maintenance issues."

Those amps are made pretty well. If you need more power, it would probably be a better choice. I had the 0 and was rated at 40 watts/ch. It was a very powerful amp. It easily drove my old B&W 802 S3's and my Martin Logan SL-3's. I put it next to the 3 and the 5 and it definitely had more power and I thought the sound quality was better as well.
While the Aleph's run hot, I would not worry about their longevity. Eventually, you'll have to replace the supply caps but that's about it. Nothing else to adjust.

And they do put out more power than the First Watt amps.
This is very thoughtful and reasonable feedback. Thanks and I will read up on them. My speakers are the older B&W Matrix 803 series 2. 8 ohm speakers, 90 db sensitivity. Keep the feedback coming if anybody has anything to add.
I've owned the Aleph 3, 30, 60s, and 2s. And an X150.5.
I also owned the Aleph J2. It sounded good.
I bought an XA-30.5 from a friend, recently.
For the money, I like the XA-30.5. It's true Class A, and it will drive almost any speaker, for a little bit more money (used) than the current First Watt amps.