I will say that you are at a point where you could do this very seriously, or just put in the most basic stuff you want. If you are able to wire yourself, then why not actually wire it seriously?
The 5.1 (or should you wire for 7.2?) in the great room is a good starting point, likewise putting some speakers outside and in the garage. But, why stop there? Where else in your home do you think you might want to listen to audio at? I got to prewire my home, and I went ahead and ran speaker wire to the office, dining room, kitchen, all four bedrooms, the master bathroom, kids bathroom, guest bathroom, front porch, etc. In total there are about 18 different zones of audio possible in my home. Anywhere I MAY want to listen to music, there is wiring in place and several of those zones do not have speakers installed, but have wiring waiting in the ceilings/walls for me to use later if I want to.
For wire, I would recommend a 14 gauge wire everywhere as most of your runs will be fairly long or have need for greater quality. Bose is NEVER the answer, and you can get much higher quality through cheaper in-wall/ceiling speakers than you will through most Bose speakers, plus they leave no footprint in the room at all.
You will want to pick a location to put your audio distribution equipment which is centralized and has the space to support all the gear you may want to install.
You will want to make sure you have cat-5 run to potential keypad locations in the rooms so that you can add local control at some point.
Outdoors, you will want to consider how many speakers and of what types are necessary to fill the space with quality audio. Outdoors can often require 4+ speakers plus a subwoofer or two for quality outdoor audio.
Wiring, overall, is cheap. It's one of the cheapest aspects of new home construction if you can do it yourself.
250' of CL2 (required for in-wall installation) rated 14/4 speaker wire is a bit over $100...
For only $97.75 each when QTY 50+ purchased - 250ft 14AWG CL2 Rated 4-Conductor Loud Speaker Cable (For In-Wall Installation) | 14AWG Loud Speaker Cables
500' of CL2 rated 14/2 speaker wire is about $110...
For only $105.36 each when QTY 50+ purchased - 500ft 14AWG CL2 Rated 2-Conductor Loud Speaker Cable (For In-Wall Installation) | 14AWG Loud Speaker Cables
Cat 5 is only $80 for 1,000 feet.
For only $77.39 each when QTY 50+ purchased - 1000FT 24AWG Cat5e 350MHz UTP Solid, Riser Rated (CMR), Bulk Ethernet Bare Copper Cable - White | Cat5e UTP Solid Cables
While cat-6 will run you about $110...
For only $105.40 each when QTY 50+ purchased - 1000FT Cat6 Bulk Bare Copper Ethernet Network Cable UTP, Solid, Riser Rated (CMR), 500MHz 23AWG - Blue | Cat6 UTP Solid Cables
You can also pick up all the low voltage rings at Monoprice for next to nothing...
For only $0.56 each when QTY 50+ purchased - 1-Gang Low Voltage Mounting Bracket - Nail-in Type | Low Voltage Mounting Brackets for Wall Plates
Now, all of this is about your home, the number of years you want to be in it and how much you want to make it YOUR home. Pre-drywall is a glorious time for anyone who has given any thought at all to installation of audio/video. It's the one and really the only time where you have a blank slate that lets you do whatever you would like to do, free of the burden of drywall cutting, drywall repair, and repainting. No furniture, no worries at all.
In two days with a friend helping you, you could likely wire your entire home, top to bottom and put conduit in place with a dozen phone and ethernet drops throughout your home easily. Throw at least 2-3 pieces of cat-5/6 between your central equipment location and the TV locations for future LAN/Video connectivity options. Wired networking is far more reliable and video over cat cabling is getting better all the time.
Consider running conduit into the attic to add more cabling later if necessary.
You are seriously looking at about $1,000-$2,000 of cabling and you can wire your house up to give a phenomenal integrated audio/video experience if you want.
One of the big keys will be your central equipment location. You want this area to be properly conditioned so gear doesn't get hot/cold. You will want it to be large enough to accomodate all the equipment you will start off with, and may want in the future. You generally don't want it in a open living area as then you will have to box it into a small console when your wife yells at you... It will also generate heat, lights, possibly some noise (fans), which isn't ideal.
If you can post the photos on one of the photo websites, then you can put the link up - put a space or something between the link so that people can figure out where we are supposed to go to see the pictures.
It's a very rare case when people can do what you are doing, and it's well worth it to do it right, right now.
As for electrical: You may not run wires to close to electrical, they should be about a foot away if possible. Run on opposite sides of studs with 18" clearance when possible. When they cross, try to put space betwen high and low voltage and cross at 90 degree angles. You may NEVER pass through the same hole as a high voltage cable.
For a receiver: Don't ask now. Ask when your home is built and once you truly have finalized your plans. It may make more sense to use a speaker distribution system, a separate amplifier, or any number of other options to get the most out of your system.
Volume controls with IR repeaters in multiple rooms with a dedicated amplifier can give you better quality for not a ton of money than a receiver which is losing power to other zones then dies early because of the drain from the other rooms. Think of a receiver as almost always being for your surround area, while the second zone output, if you buy into it, provides a feed to your dedicated whole house amplifier.
