The Powermax in the link above is a well regarded version of the stock turbo, but having a larger impeller it needs to be run with a tune. So you have to add the cost of the tuner and the software to the cost of the turbo. Then you get into the whole head stud thing. I wanted to remain stock, but to try an aftermarket turbo since the truck has had two Garrets. If you don't drive them the variable vane system tends to rust up and stick, and I left mine parked outside all winter, didn't even use one tank of fuel, so it was my own fault. You have to drive these things regularly...
Brian