I made a spare bedroom into my media room. About 5 years ago, and i wanted 90-100 inches. There are trade-off's with projectors, but they are worth it. But I spent a bit over $3K on the projector and screen.
It's tied directly to how big you want to go and for what $$$. When you go over 65"+++, the cost for any Plasma, LED drastically climbs; and you are at (or close to) what a modern projector runs (Assuming you don't buy the cheap crap).
If your budget is $800, then you got only two roads. Buy a new 50-60" TV (Plasma/LED) or buy a used projector (I wouldn't...the bulb alone costs $200, and is probably going to go out).
Go buy the biggest led/plasma TV you can afford. At around $800-1200, its your best option.