I understand the DIY allure, I really do (I do some electronics DIY myself - guitar pedals, tube amps, that kind of thing), but if you want to get great sound and save money at the same time, then just get a used QSC amp from Craigslist for $400 or so. It's better than pretty much anything you'll be able to build on your own for "reasonable" money, and it doesn't look "DIY".