I just went through all this last year for the first time.
Learned a lot, for the most part it was enjoyable. I was the general and subbed out everything.
On the wiring.....I agree......don't run wires except standard telephone, power and cable. And here is where i did stuff a little different.
I knew where I wanted or might want TV's on the wall. I had power put in behind where the TV would be and also on the next stud had a dummy elec box put in......then ran PVC pipe down to another dummy box that was the standard height of elec plugs(18" i think from the floor). I also had power at the 18" height too(1 stud away) and cable. Most people have cable or Sat boxes......and most TV's these days are either HDMI or Composite inputs. So you will need to run your HDMI cable from your cable box that is most likely a couple feet off the floor on a piece of furniture up to the back of your TV, the only way to cleanly do this is to use the dummy boxes to fish the HDMI cable through the wall. In summary.....at 18" height have Cable, Power and Dummy box(One on each side of 1 stud, 1 on the next nearest stud). At 5ft(or whatever you decide) have 1 power and 1 dummy. Connect dummies with 2" PVC(to allow for large connectors). You will have to cut the bottom or top out of the dummy boxes and just set the PVC on top of each and I held it in place with the metal tape with holes that screw to the studs.
You might want to consider having the top elec box recessed a little depending on how close you want you LCD to the wall.
And remember you can always cover up the top boxes with a picture if no TV is in the room or you put multiple TV locations in a room but only use 1 of them but allow for future possible re-arranging.
I did this same sort of thing where I knew my stereo receiver was going. Large PVC pipe to attic to allow for speaker wires to travel throughout the house easily and allows for addition and removal when required(unlike fixed cables in the wall).
And the Cat 5 thing........everything is going wireless. I wouldn't worry with it.
Insulation. I did the sprayed foam on exterior walls and attic decking. I love it. I have a single story(slab) but tall roof line and my attic is usually only about 5 degrees warmer than the inside of my house.....which allows you to store anything up there without the fear of heat/cold damage. In fact I keep my cable modem and wireless router up there....as well as my main security system box and my phone modem. All out of the way.
Other things you might wanna do:
-Smoke detector in attic. (i have my furnace and HW heater there)
-Add power in attic to support above items if you desire.
-I went with Tankless HW heater......love it. Rinnai 94 NG.
-Never pay until it's done.....make this clear up front. Your better contractors will not have a problem with this. And try to pay 85% when it's done and the rest like 2 weeks after you move in to ensure they come back to fix the little stuff which they hate to do....again, talk to them and make sure this is clear up front.
-I did PEX piping.......second house i've had PEX in. I like it. Some plumbers don't, some people don't, research and decide.
-If you have not found a place to build consider these things:
inside or outside city limits?.....in my area the cost for building permit changes depending on if you are in or out. Also, outside you will incur septic tank system costs, vs city sewer tie in. Possibly same issues with power and Nat gas. Keep these things in mind.....especially if you have two properties that are a "toss up" maybe the expense difference will help you make a decision.
Is that all you expect to get out of your houses? Bricks and motar guys, lasts for hundreds of years! 