Care to share any listening comparisons between the two? 
It's a bit hard to tell since there was a long period of time between sending off my preamp and getting it back with the upgrad. (AVA was really busy at the time.)
With that in mind, I feel the OmegaStar had excellent bass and mids, but could sometimes sound a bit hard in the treble.
The Insight upgrade completely solved any problems with the treble. It also seemed to reveal extra layers of detail, without ever over-accentuating anything. I remember thinking at the time it was as if another veil had been removed. I wasn't aware of any real problems with detail or lack of it when I had the OmegaStar, so it was quite a surprise to get the Insight preamp and hear all that extra detail.
From there, the Insight+ mini-upgrade seemed to make the preamp quieter yet. It also seems like things like the kick drum became a bit more solid-sounding.
I wish that I could have some of Frank's older SS designs in the same room as the latest ones so that I could do a proper comparison. It would be interesting to see how things have evolved over the years.
I do have an old SuperPAS and an FETValve amp. The PAS is quite colored and the bass and treble are weak as well. But it has the original Dyna filter cap and I'm sure the cap is on its last legs at this point, so it's not really fair to compare it to anything.
The FETValve amp isn't bad at all. There's a bit too much mid-bass, and it kind of muffles the dynamics of things like a drum kit, but overall it's still pretty good. I think I could live with it if I couldn't have my OmegaStar amp.
