A drummer came in here a while back with a set of e604's from Sennheiser and I had never really even seen them before. I was quite hesitant to use them instead of our 421's, but when I armed the tracks and heard the sounds I was sold. Great mics for the money, for sure. I was originally going to just tell the guy they were too crappy so that I could use our 421's, but like I said, I was extremely surprised at how good they sounded. Honestly after that experience, I don't know that the $300+ tag on each of our 421's is justified. I'm getting the e604 3-pack + 2 more for my studio to use on toms. The built-in clip is really cool too...I only had a stand for the snare, ride, hats, kick, and OH's....imagine not having 3 more stands...or usually what I get is 5 toms in a kit with these metal heads around here. That's 5 less stands I have to worry about. Yummy.
421's are good, don't get me wrong. It's just after that, I don't know if they are worth their price. I've done the Chili Peppers thing before as well, using all SM57's on the toms, worked out cool...but it's actually hard to make it work in every situation with all 57's...it can work though, just takes more work with certain kits/styles than others.
~e.a