Cat - check out projectorpeople.com. I got a great deal on a PJ there. You can actually call them and speak to a live person, too. They have lots of PJ's set up in their showroom and are knowledgeable enough to give you advise on what will fit your needs/budget. They are a lot more than just a wholesale/retail depot.

Also, I would take the opportunity to invest in a nicer screen now (assuming you have the cash on hand) rather than buying it twice. As for the PJ, there is something to be said about getting a "low-end" 720p PJ and upgrading in a couple of years.

On the other hand, if you're tempted to hold off on buying the screen, you might try to simply paint a white square on the wall that matches the PJ picture as a temp solution - not great, but it's a pretty good facsimile of the real thing.