1) I've looked at a bunch of different companies and the rogue racks are the best value by far, if you're wanting new equipment. You may find some cheaper alternatives but the quality/strength won't be there.
2) Also, I've always heard the SSC's say don't skimp on the bar. Rogue sells a B&R bar which was designed by Burgner and Rippetoe.
3) If you're just wanting metal plates, keep an eye on craigslist
4) They're is a great SS article on building your own platform
5) Definitely listen to the last few barbell Logic podcasts. They had the guy from GarageGymReviews on... Lots of good content