I purchased an Ultimate PS with Bybee shortly after your original post, and now that it's had some time to break in, I can offer some comments. I was running an SB3 with Bolder digital mods and an Elpac PS modded by Bolder that I had purchased used. I opted for the digital only mods because I had added a TACT 2.2 Mini room correction system after experimenting a bit with the Inguz plug-in using some really low-end measurement tools and concluding that I could really benefit from some room correction. Since it will be years before I could ever rip all my CDs for use on SB, I wanted a room correction approach that would benefit both SB and my Meridian 508 CDP.
With the modded Elpac PS, the SB3 performance was close to the Meridian, but a little muddier sounding. Some details that I'd hear on the Meridian were missing on the SB3, and the Meridian bass was noticeably tighter. I noticed no difference in the soundstage.
When I first plugged in the Ultimate II PS, I immediately understood what the term 'black background" meant. With such a quiet background, instruments and voices were much clearer and more detailed. Now after a few months of break-in, I can say that the SB3 is more detailed than the Meridian CDP and the bass much tighter. I don't notice a difference in the width of the soundstage, but with the SB3, I get a greater sense of depth of the soundstage on many recordings. It seems as though the blacker background makes it clearer where each of the performers are placed on the stage, from front to back as well as from left to right. So now more that ever I'm anxious to get at least all my A-list CDs ripped for use with SB.
I haven't heard the Ultimate II without Bybees, so I can't help with a "with and without" comparison, but I can tell you that I'll get my money's worth of enjoyment from the Ultimate II PS with Bybees.