I recommend investing half of your budget in a solid set of quality speakers. A good set of speakers will last you 25 years whereas your player/projector/receiver will get outdated within a few years and you may want to replace it with something else.
I've heard good things about the rocket line of speakers
I've heard SRS makes good subwolfers. Go to AVS forums and give them your budget, they'd know more about what you'd need better than I would.
You are going to get a better movie experience if you buy a projecter/reciever/standalone player (at this point I'd just buy a blu-ray player)/and speakers as opposed to a computer HTPC setup. The tradeoff is that you won't be able to do computer stuff on your HT setup (unless you want to buy another computer in addition to all that stuff).