When I purchased dedicated regulators for my doubles I strongly considered the DiveRite, Zeagle, and Apeks. I ended up with the Apeks because the initial price for all of the regs I was considering were pretty close and Apeks has the "free parts for life" thing, the others do not. I also like the way the dive/predive control works on the Apeks and Zeagle. The DiveRite has the little control on top and the internal workings of this control are different, I don't know if it is any worse, just different and I like the other way. My opinion of the three first stages, the Apeks ATX50, the Zeagle ZX-50D, and the DiveRite RG2500ICE are all alarmingly similar, and the second stages are also excellent, the only major difference is the dive/predive switch on the DiveRite.
I have seen all three brands used in caves, and would have no reservations about using any of them myself. You are considering some top regulators so look at the details surrounding the edge of the deal like maintenance costs and ease of getting them serviced or obtaining parts if you plan on doing it yourself.
Mark Vlahos