No sure where's you're located but Sound Advice, a Tweeter company, is closing all it's locations nationwide. The deals they're giving on their equipment are stellar and only getting better as the liquidation sale goes on. I would check their web site, tweeter.com, for locations and see if you can pick up some of the equipment there. It will definitely make your budget go a lot further.
As for your in wall/ceiling speakers. I have Sonance Symphony speakers in my house and have been very happy with them.
As for wiring, there may be a better way to do it, but this is what I did:
Every location that has a screen, TV etc., got 4 RG6 coax and 4 CAT5. All runs were homerun from the main AV closet to the locations.
Every room got a drop for a volume control with 2 CAT5 cables and then speaker cable. The speaker cable basically went from my AV closet to each volume control, but was not cut or terminated just looped, and then run into the ceiling to blank boxes, which would act as placeholder for speakers to be added later. Because I didn't know what volume control etc. I was going to use, this gave me the option of powering the speakers directly from the AV closet, which would then leave the speaker cable untouched, or would allow me to us volume controls in the rooms, in which case the speaker cable was cut and terminated at the volume control.
Because I built my house pre-HD, I would also consider where you would like to watch HD and whether the source would be local or not. If the source is in an AV closet, you need to weigh the options of running HD over coax/cat5 by using a balun or now running HDMI cable etc. from the source to the screen. I didn’t run any HDMI cable and am not having issue re-wiring.
Also, you will want to run drops for any dedicated HT setup, for your speakers and sub.
Lastly, the coax/cat5 drops I put in were because all my sources are in one location. If you're going to share sources (eg: the cable box in the game room will also be seen in the office), you will need to add a dedicated run from that source back to the other location.
I ran everything to a dedicated AV closet, which allows to “share” sources but also make changes fairly easily.
Your best bet is draw a diagram of how you plan on "sharing" equipment across the house and when in doubt put in extra wire, that's the pars that is cheap now while the walls are wide open.
Good Luck
