Just as a testimonial, I'd like to say I put a Diamondeye 4 inch on my 97 dually a couple years back. I heard some good things about it, but the price was the deciding factor. Paid $295 shipped from some shop on ebay. I found it to be very easy to install, and as for the sound? I simply cannot say enough about how awesome it sounds. It sounds like a big tough V8 is supposed to, without being too loud or droning. I don't like real loud exhaust, but I want it to be known that there is something under the hood that means business. I had a Banks 3.5 inch system on there before, the muffler rotted out first so I put in a piece of test pipe and it sounded really nasty, it had a bark to it and was pretty mean. Maybe just a little too raw, but I liked it anyway. I really wanted to leave out the muffler on the DE, but I was afraid it would be louder than the Banks, and if anyone looked under the truck they could see it wasn't legal. So what I did was put the straight-thru muffler on backwards, so the little louvers wouldn't do anything. My only regret was that I could only really hear it when it was warm enough to keep the passenger window down, or when I let someone else drive it. It did sound pretty awesome under WOT when it was passing me in my 454 truck. Yes, it passed the 454. Didn't think it would, but it walked it like a dog.
I wish it had come with a bung for the EGT gauge. My Banks system came with one, I threw it away before realizing I couldn't hook the gauge up. Ordered a new one from Banks (sent it to me free, even after several years had passed), but it didn't seem to be the right one for the gauge. So, it never got hooked up again. Don't have a gauge yet for the Suburban, but hopefully when I get one it will come with a bung.
I do want one for my Suburban, and I will definitely be buying a DE again, so I'll order it from Burning Oil to keep it in the family. Unfortunately it's been back-burnered due to financial ruin.