well that's a different question than the title. You asked top tier regulator brands, but are missing Poseidon, Argonaut, and Deep 6.
Several other manufacturers left out as well including Hollis so it is not a comprehensive list of manufacturers.
You list a budget, but the "top tier" regulators from most of those manufacturers are considerably more expensive than $550 for just a first and second stage, so do you want the best value regulator at that price point, or do you want the best of the best regardless of price?
Apeks XTX40/DS4 is $570 and is pretty much the bottom of their regulator list, but their "top tier" is the XTX200 at $800.
You list regulators that I would certainly not consider "top tier" from a quality standpoint like Oceanic, but then leave out one of the highest quality regulator manufacturers with Poseidon.
1- performance from brands like Deep6, Poseidon, Scubapro, Apeks, and Atomic can't really be beat, but the others are like 90+% of the way to those performance specs so that's all a wash
2- that is largely a function of the mouthpiece that is used and whether it is comfortable to you. Things like swivels/elbows are universal, braided hoses are universal, etc. so that is all a wash
3-Most of them are pretty darn durable as well so you aren't going to have a lot of differentiation. I am a Poseidon guy and you'd be hard pressed to find anything more durable than the Cyklon which is why it is used in sump diving, but that doesn't mean you can't knock someone out with a Dive Rite XT and not change any of its performance
4- Purchase prices are all over the place for the brands you mentioned and maintenance costs are largely identical if you're going to a LDS for factory service, certainly within $10/stage as the labor is all usually fixed price and the parts kits are all about the same price.
5- brand warranty and CS is something that will actually change. I would never buy a regulator from AUP due to their customer service, nor would I buy a regulator that has a warranty based on dealer authorized service at x-intervals. That narrows the list considerably for those that actually have lifetime warranties and stand behind them.
Unfortunately IMO the poll is largely worthless, and if you're trying to find a regulator for yourself, you'd get far more useful information by asking directly for it. Provide things such as location of diving, willingness to do your own service, travel or not, ultimate goals for type of diving, what your buddies are using, what your budget is, etc etc. That can help us narrow down and provide you with some more useful information.
