Hate to be a cynic but I'll be the first to say: Just sell your car, save a few grand and buy an 01 M3.
That is the best upgrade you can make to your current e46 if you want to go fast. 325s aren't fast and really aren't designed to be made fast. Sure like anything else, it can be done. Frankly, in 2008, it's just not worth the time, effort and $$$ you'd have to shell out. Unless your planning on making this thing your life's work, get a different speed machine.
*back on stock 17s, so sad.