Alright, your budget is realistic.
Now, you can go with B-stock (read: USED) Crestron gear for far less than other systems, but it is truly the wiring which you should focus on.
1. Don't just guess on this, make a list of your rooms and make a list of what you want in each room and where you want it.
2. Where you want it in the room is critical - it can't really be changed after drywall is up without significant cost, but if you may want a couple of options, then let installers know and they can make a loop between locations (ie: wall to floor wiring for your option)
3. Figure out your subwoofer(s) now. Velodyne jumps to mind...
SubContractor Series - Subwoofers - You really want to figure out in-wall or in-floor ahead of time and get things in place and this one is a tougher option.
4. Understand that speakers won't go in until after drywall and painting is done typically.
5. In-wall speakers bleed sound into adjacent rooms more, but get listening at proper ear height which can open the soundstage and preserve imaging. In-ceiling speakers bleed sound between floors more, they work well with stereo in a limited area, and tend to hotspot a bit more. But, the actual sound quality is about the same.
6. I've used speakers from SpeakerCraft, B&W, Niles, Boston, and Sonance... I keep going back to Monoprice for my general listening speakers. Their 8" 2-way in-ceiling stuff sounds good and is cheap enough that you can just throw a set up to try and compare them to another more expensive brand before you dish out thousands of dollars.
Something like this would be a cut above your typical in-wall and better for your surround zone:
CInema LCR2 | Sonance
But, it will cost a pretty penny for those. Still, it will use the same wiring.
7. Unless rooms are being acoustically treated and using really good bookshelf speakers, you aren't going to hear a difference between 12 gauge and 14 gauge wiring in your home.
8. Amplifiers are all over the place in quality, but Rotel makes some good stuff IMO. There are certainly other brands out there, but the quality will cost. Most of all - it's something which can be addressed at a later point.
9. Be aware that the typical keypad now, and in the future, will probably run fine on cat-5e cabling.
10. Video distribution adds a new twist and a potentially significant price tag, but may enhance the lifestyle within the home significantly. Worth consideration at least.