One thing, perhaps the primary thing, that the inspector will look for, or that you should accommodate should you choose to bypass the permit process, is the location of the panels. They'll want to see a path (I think it's 3') around the panels that can be used by firemen on your roof. They need to be able to walk around up there without slip-sliding/tripping on solar panels should they need to... A permit will likely be required, for this reason alone. As suggested, a phone call to the planning dept is all it takes to know for sure.
Heliocol was my choice. They're up there in terms of heat exchange (there may be some that are slightly better), but when it comes to ease of installation, they're awesome. I've only installed my own, so can't say much about others, but the Heliocol system is genius. Among other niceties, the panels seal to one another by way of internal o-rings, not the more typical external "radiator hose and clamp" systems, which are prone to sun damage, shrinking and leaking (from what I've read). They also use a set of brackets that allow for expansion and contraction and wind, etc. Highly recommend!
Oh, and I had a similar estimate. I did mine for half that by installing myself. It's actually not that hard to do. I lucked out somewhat in that my supplier (a local solar installer), offered to sell me a Heliocol kit. Basically everything I needed, everything they use, to install. Down to the screws, the paint, even some clean up rags! And the price of the panels was considerably lower (like 33%) of what I could find anywhere else (Walmart, Amazon, etc).
I had a pool guy connect the plumbing to the pad, because they were doing some other work for me at the time, but I probably could have figured that out, too. It is also relatively simple.
