Thoughts from Joule preamp owners?

I think the 150 Mk ll's bass is tighter and a bit more extended than the 150's loose bass.

Which 150 do you mean? The 150 MKI or the 150 SE (sorry Signature Edition,
not Special Edition)?

The 150 Mk l. The Signature Edition I've been told, by two owners that had their 150 Mk ll's upgraded to the Signature Edition, that it is an improvement in all respects. I like the way my system sounds currently and haven't wanted to play around with the sound by "upgrading".

The difference between II and I is much greater than the difference between III & SE, I think II & SE are much more musical than I, there was some change in the tubes used and possibly the circuit in the move from I to II/SE, Is SE an improvement over II, sure, a bit, but after moving from II to SE, I found that it would have been perfectly easy to live with II and be perfectly content - both are very fine preamplifiers that suit my sonic preference very well.

Good information thanks for sharing your experience!!