The only thing good about Oxycheq are their wings. The Mach V series are very good wing, arguably the best thing currently in the industry at this time. They have a 360 loop zipper so you can unzip the outer shell to access the liner for cleaning, inspection, and repairs. They are very tough, especially with the extreme series, and they are streamlined. I've been using a 40# M5 for years now (ever since they came out) and have had zero problems. I also like the fact that the inflator elbow comes out of the left side and not the center since I use a very low profile plate and don't like the idea of the inflator interfering with the regulator.
I used to be an Oxycheq dealer so I know how they are with customere service (me as a dealer). As long as I was buying and had no problems or returns, fine. But as soon as I started having problems with a bunch of lights (I was selling) they were MIA, didn't want to hear it, pretended they weren't getting e-mails, wouldn't own up to the fact that the lights they ordered and had made in China absolutely sucked! Every single one of them failed, some before they even hit the water. But that was their lights not the wings, the wings rule and as far as I'm concerned is one of the only things they have that is of any value. Their harness kits are good too. The only thing about them is I don't fully care for the buckle but it will do. For a while they had some really stout ones that were great, but I haven't seen those in a long time. Their cam bands are OK but I like the Dive Rite ones better. They are the same buckle and band (made in the same plant) but Dive Rite has a better tank protector cushion that they added so the tank doesn't get all scarfed up when you snap the cam buckles down.
Oxycheq plates are just generic plates like anybody else, nothing particularly special about them. Any plate of that type will do. Dive Rite has good plates if you can get one somewhere at a decent price. So does DRIS or Hog or many others. I'd just shop for price on the plate because once they're set up and on your back you're not going to be able to tell the difference from one to another. They are all slightly different in outer shape, bend angle, etc., but the differences are so slight it's not day and night by any means, and for all practical purposes is undescernable.
My last piece of advice is to just get a simple one piece Hog harness (one continuous length of webbing with a few D-rings). You don't need the fancy deluxe harness. It gets away from what the whole concept of a BP/W is supposed to be in the first place, simple.
You also don't need a STA, teh Oxycheq wings have side cushions that line up the plate to the wing/tank and everything centers up when you cinch down the cam bands.
Good luck!