I had intended to post a follow-up review to this thread detailing my experience with the Deep6 Signature regs. However, that is somewhat complicated by the fact that my experience with regs has been limited to cheap rental regs previously. My diving also has not approached anything that would challenge any reg. So this "review" is just closing a loop for me, as value in reviews goes. But, for what it is worth:
I really like my Deep6 reg set. The build quality feels topnotch and the performance feels the same. Comparing these to rental regs I have used is like comparing a rusty Ford Pinto to new Audi. So I am not even going to try. All I will say is that I like them a lot. I think it is a little like talking about cornerbacks in the NFL - you normally know your team's CB's are good because you never notice them; they shut down their receiver assignment and nothing else happens. Regs for me are like that. The only thing I noticed for the Deep6's was the mouthpiece - and I tried the Aqualung Comfort fit mouthpiece and didn't like that one any better. (The quality of the included mouthpieces is fine - it is just a preference issue.) Otherwise, the regs gave me my air and got out of the way. (Unlike the rental regs, which wheezed like a 90-year old chain smoker sprinting from Godzilla at any hint of heavy breathing.)
I will also say I really like how the SPG dial is marked. I had a dive buddy who was a little jealous of how good it looked while glowing on a night dive. Nothing bad about having an SPG that you actually LIKE to look at, lol.
The useful point is I am happy I went with a Deep6 reg after a summer of diving. Not much of a review, but it's what I got.
Happy diving.