Sounds like you prepared yourself well and did your homework. First things first, I would get at least three bids for your sprinkler system, because it will better help you decide in coming up with a median price for your new sprinkler system.
As far as parts go, each contractor has their own opinion as to which products are the best. I personally have never installed the Irritrol products, but I have serviced them. Both Hunter and Rain-Bird make excellent products, and they stand behind them. I am an exclusive to installing Hunter products, so I know a lot about them, and I highly recommend them.
For your backflow device, I have always installed the Febco brass backflow units, and have had very good experiences with them, I haven't used the Wilkins products before, so I couldn't give you a run down on those.
For the sprinklers, both the PGP and the I-20 are excellent heads, with the I-20 being built a little bit tougher than the PGP, and a few extra options. The I-20 also carries a 5 year warranty, whereas the PGP carries a 2 year warranty. I used to install the 1800 sprays from Rain-Bird, and they are alright, but I now install the Hunter Pro Spray heads, which I think are a lot better built and have a better spray pattern than Rain-Bird.
For the valves, again I haven't used the Irritrol products, but it seems like I do service them an awful lot. We install the Hunter PGV Jar-top valves. They are a high quality valve, and it is very service friendly.
For the controller, the Hunter SRC is a good controller, but is only available in 6 or 9 station, indoor or outdoor. A fine controller for smaller irrigation systems, but if you ever expand beyond 9 stations, you'll have to upgrade your controller. We generally install the Hunter Pro-C , which is expandable up to 15 stations. The Hunter controllers are very easy to use and program, and have a non-volatile memory, which means it will retain its program information during power outages. All Hunter controllers come with a SmartPort, which can be installed for remote control options, as well as other attachments. Also, all Hunter controllers have the capability to support rain, wind, and freeze sensors.
Finally, as for your piping, because you are in New Jersey, a freezing climate, I would suggest the use of Poly pipe over PVC. Up here in Michigan, Poly pipe is all we install. It stands a much better chance in a freezing climate than PVC does.
Make sure you feel comfortable with the contractor you choose to install your system, and make sure he or she has references. Good luck with your system, if you have any other questions, feel free to ask.
Tony Posey
Ridge Run Landscapes