Short Version
Call or email Tobin at DSS and have a conversation. He truly is the man.
Long VersionI have dived several different BCs and currently dive a BP/W set up (DSS BP/W and a DUI Classic harness for my weight belt). I spent a lot of time on research and am very happy with my set up. Fit was insanely good. And the plate (even diving in a t-shirt was comfortable) with no padding!
I would encourage you to call/email Tobin at DSS (more below).
Background:
A BP/W consists of three major components: the backplate, a wing (the floaty thing) and a harness. The simplest harness is a called a Hog harness.
For a plate, there are two choices: light (typically Kydex or Aluminum) and heavy (typically stainless. Plates may come in a variety of sizes to fit different divers (short, tall, big, etc.). If you use stainless, you can typically take some lead off of your belt.
For a wing, you need one size to your needs. Avoid anything that pretends to work on both singles and doubles. I also avoid bungee wings. Your wing needs to be able to do two things: a) float your gear with a full tank and without you in it; and b) float you at your heaviest configuration such as with a full tank and a compressed suit.
For a harness, a Hog is simple and, I found, perfect for me. It is simple: a single length of resin impregnated webbing, some d-rings, some tri-glides (weight belt keepers) and a weight belt buckle. There are other options but I would start simple and see if that works.
Then there are the other minor pieces to the kit that I think you need. First is a crotch strap. While it sounds strange, they are a great thing. I would not use a BP/W without one. Second is two cam bands (assuming you are diving singles) to attach the tank to the plate. Third is some some little rubber blocks that help keep the tank tight. Depending on the system (DSS singles wings and some Oxycheq don't require this), you may also need a STA (single tank adapter).
Then there is the other stuff you can add. Back pads, shoulder pads, pockets, etc. IMHO, these detract from the rig but to each their own.
Why DSS?
First, they have really well thought out and solid gear at a very fair price. Second, they have many options around plates. Third, they have great customer service and provide great advice. Finally, they really make it easy.
For example, they will sell you an entire kit. It comes with a plate (size/material of your choice), a wing (model of your choice), Hog harness (tri glides, d-rings, buckles, webbing, etc.), two cam bands with elastomer blocks, inflator hose (with their quick relase handle) and crotch strap. I think you also get a DIR knife. Their wings do not need a STA (at least the ones I looked at as well as the one I own). That is everything you need!
They will also take the time to figure out what will work best for and they will not sell you stuff you don't need. The cost may seem steep but when you start adding up all of the bits it is a really a very good orice.
Other
Other brands besides DSS? Lots of very solid brands. I own an Oxycheq wing (as well as my DSS) and it is also a great peice of gear. Halcyon is also great (but at a premium price). I would personally stay away from OMS. No first hand experince with other brands.
I would also look through the Equipment/BCs & Weight Systems Forums.
