Hello Ethifi,
I have not heard the ASL but we have the same genre of music that we prefer or listen to. If you happen to read my review of the stock S-250, I had the opportunity to compared it to several tube amps.
I too have the Supratek (Chenin)and I can assure you that the preamp is a very good match to the ICE H2O amp. Come to think of it, all the amplifiers that spent some time in my stable sounds good with the Supratek. But that is another story.
One of the many strenghts of the Supratek is how good it delivers the bass even as a tube preamp. You know that, and I am pretty sure that you are confident to say that the preamp does everything well. With the ICE H2O being driven by it, it makes the qualities of the preamp shine to the fullest. The sound is so clean (noise floor) but not devoid of the subtleties that makes the voice enticing and warm. With the H2O, you will hear a different presentation of the bass as the amp projects it. For me, it is the best acoustic bass I ever heard my system can reproduced. With my Magnepan 1.6QR, I de-commisioned my two (L and R) Adire Audio Rava designed subwoofers because in two channels, I do not need it anymore.
Another thing is that the ICE does not produced any thump even if you turn it On ahead of the preamp or shutting the preamp Off while the amp is On. Try that with a tube amp and you will probably re-create a mini fourth of July.
ICE have a trial period. I would suggest to take advantage of it and see if it floats your boat.
best,
Abe