The question you asked is subjective. The answers that you receive will often be along the lines of 'well, I use an Apeks, so that's what I'd recommend...' Of the regs discussed, the only regulator I wouldn't purchase is Scubapro. Again, this is based on personal experience; someone else might have an opposite view. I've used and owned several brands of regulators over the past 48 years. Currently, I prefer Apeks when using open-circuit.
I wouldn't be concerned where you purchase your regulator. In-fact I'd look for something used, if it was me. There are many divers who learn to dive, buy equipment, dive a couple of times, and move on. There are lots of regs out there that have less than 20 hours on them. Take it into the LDS and have it serviced. You just saved yourself money that you can apply to something else.
Anyway, just another perspective... Buy a name brand reg at an excellent price. In today's market, I wouldn't buy anything used unless it was still in the box, or I was reasonably assured that it was only lightly used. Although a reg that has been used a hammer will likely work well after service (that's a bit exaggerated, but not far from the truth).
You don't need a new reg, unless you just like to spend money or get a really good deal.