Hi Travis, welcome to diving. First off let me say that the two brands you quoted are very good and they both have decent lines within them. However being established brands means that a huge part of the price goes to pay for the opportunity to use that brand. I cannot say that I have used any Zeagle regs as I have no diving friends who own them. I have tried breathing from Apeks regs and I prefer the ATX 100 to the XTX 200. That said the XTX line has one very useful feature if you see yourself getting into sidemount diving, the LP hose can be mounted on the left side of the second stage. Also, the XTX line have relaceable exhalation diverters. Should you find the standard pieces too short you can remove them and attach the extended(longer) diverters.
On to other brands. If you are dead set on having diaphragm regs it would be well worth your while to consider HOG D-1s as well. Their first stages are similar to the Apeks DST and the flow rate is just as good. The D-1 second stage is an Apeks clone but actually operates more smoothly than the Apeks regs I have tried albeit the the spring tension adjustment is not as genrous as that of the Apeks. Upon bench testing both brands the HOG D-1 actually "cracked" sooner than the Apeks which translates into lighter inhalation effort. I am sure the Apeks could have been adjusted to crack sooner but that is how the reg came out of the box. Another thing worthy of note on the HOG D-1s; these regs are being marketed specifically to the tech diver. They encourage you to learn how to service your own regs and Dive Right In Scuba(DRIS) is teaching that regulator service course.
Piston regulators on the other hand have the advantage of being gas flow kings and of all the brands I have tried(Atomic, IDI now XS Scuba, ScubaPro, etc.) the latest offering from Sherwood, the SR-1, has the lightest breathing effort I have yet experienced.
Presently, I am using IDI Seaira firsts coupled to HOG D-1 seconds. I can't quite afford the SR-1at $610 a set. The D-1 firsts were O2 cleaned and are now serving as deco regs coupled to either Poseidon Jets or Atlantis(Tilos) seconds.
BTW, the low end of the budget you quoted is enough to set you up with a doubles reg set-up(2 firsts, 2 seconds, 1 SPG and the attendant hoses) at DRIS. Below is the link for this offer.
http://www.diverightinscuba.com/catalog/doubles-package-p-2596.html