I am in the middle of a very similar purchase/build right now.... take a look at the ebrewsupply 20amp 120v rims DIY for ease of sourcing some of the small parts.
http://www.ebrewsupply.com/1-pid-20a-120v-rims-kit/. You will still need to source a PID, enclosure, and power inlet and outlets, temp sensor. He provides the circuit diagrams that correspond to the equipment, and are fairly easy to read.
Hunt down the RTD sensors early, especially if your are looking at some of the china options, they work but shipping takes forever.
I purchased this, and the RimsRocket, for the same reasons you listed above. and also I liked the more complete feel of the RimsRocket, with its molded grounded plug, and purpose built connectors vs the Rims tubes with HD elements, and wiring. Wiring is nothing new to me so that part doesn't worry me much. The ebrewsupply kit says it is rated for 1 2000w element and 2 pumps. I will be running 1 pump, 1 element (same setup as yours for boil and strike/sparge water).
(I have the advantage of already having a pre-wired, 2 circuit, 20amp 120v twist-locked run in my brew space, so I will be running two circuits to my panel anyway just in case I want to run an accessory outlet off my pump, and just have build an extension cord, and put two GFI breakers in the panel.)
(Just a hint, don't forget the cost of the ancillary's, i.e. wire, ties, mounts, inlet and outlets, those add up fast, and quality electric parts run nearly the price of the main parts. I did, and it really smacked me in the face, even when purchaseing through the supply house I used to work at.)