Which Moscode 300 vs 600

I have owned several Moscode 300's from stock to maxi to modified and at different degrees and levels. I am going to look for another Moscode for my system because I do like their sound. I want any input from those who have owned both the 300 and the 600 models. I borrowed a 600 and found it to be a little more lively sounding and not as airy as a warmed up 300. Maybe a little more analytical sounding as well. Any opinions on the 600? I know the 300 pretty well. Does a modded 600 change the nature of the sound from the stock model?

Power is not a big deal for my application.
Interesting that you found the 600 "a little more lively...and maybe a little more analytical" than the 300. A number of years back I owned a pair of the 300s(which, as you know, were hybrids). I also had the opportunity to give a good listen to the 600 on several occasions. I found the 300 considerably more involving than the 600. In fact, to my ears, the latter didn't sound lively at all, but rather disappointing and a bit slow by comparison. I heard both on my Dunlavy SC-4 speakers, which were and are(I still enjoy them)quite revealing. Incidentally, an overwhelming majority of my listening has always been with long play vinyl records. I assume you'll give both amps another good audition in your system before you make your final decision. Ahh, but I do fondly recall those Moscode 300s. Good luck and good listening!
I guess my experience was 600 reminded me of a solid state sounding amp. I have Dunlavy Cantatas which have the same basic drivers as the 4A. I am thinking the 300 is my best bet from my own experiences but had to ask since my 600 experience was brief.
Actually, the 600 didn't impress me as sounding solid state at all. Though I have long preferred tubes to transistors, the all tube 600 just sounded comparatively lifeless to me. And as much as I enjoyed the hybrid 300s, I have since never owned another hybrid amp. My modified Air Tight ATM-3 tubed monoblocks have served me well for a long time. Based on YOUR current feelings, your ultimate decision should be an easy one!
Owned both. Stock, and modded. I agree with Opus88 that the 600 sounded somewhat lifeless. During all the years that I owned the 600, I could never understand the AHC review in TAS in which he describes the 600 as very dynamic. I would have to disagree. It will play very loudly as it has tons of power, but the music does not MOVE. It sounded somewhat "lifeless". So why did I keep it for years? Beacause it was a very full, and robust sounding amp with nice tonal colors. This was exactly what my Maggie MG3a's needed to not sound too thin, and it was all I could afford at the time that had that kind of power.

"Does a modded 600 change the nature of the sound from the stock model?": No, but it will be a little more refined sounding, and maybe a tiny bit more agile sounding.

Interesting that you found the 600 more lively sounding. In my experience the 300 sounded a little more agile than the 600 (maybe your speakers really need the extra power). But I don't think that it was the result of actually being a faster amp. The 300 was not as full or dark sounding as the 600, and the psychoacoustic effect was of being "faster". An Olympic sprinter running the 100 yard dash, would probably look to be going faster than an NFL linebacker running at the exact same speed.

BTW, the 600 gave me one of the most important and memorable audio lessons: I bought a pair of incredibly difficult to drive Stax F-81 electrostats. I thought that the very powerful 600 would be just the ticket. The sound was mediocre at best. One day, a friend brought over a lowly Dynaco ST-70 pure tube amp (35W/ch) in stock form. The Dynaco blew the pants off the Moscode 600. I could not believe it. All of a sudden, there was refinement, and although it would not play very loud at all, the music MOVED. It was an incredible experience.

The Moscode was treplaced by a Berning 1001 (?) pure tube design, and I never looked back. (Manley's currently).

Good luck.
Many (many) years ago, before knowing HR, I borrowed a 600 for a week to drive my Infinity RS2bs. Reading the above posts was like going back in time. I concur, through the cloud of my memories, that the 600 was indeed lifeless. It made music, but not magic. I so wanted to like it. There were many great reports on it. In fact, as I look back on it-- it was the first time the reports and my ears did not agree. Perhaps that's why I became a reporter.
Thank you all. I will wait out the storm and buy an amp that is right. I am trying to power up a pair of Dunlavy Cantatas and I think a good tube amp will be the sound I want. Just sold a Belles ( phenomenal!) and have decided to switch back to tubes for a bit. Thanks!!!!!!!!