2000 Silverado 4.3L Lifter Problems

I have a 2000 Silverado with the Vortec 4.3L V6 and I have a loud tapping, very loud on start ups but quiets down after awhile. I have gone to several garages and they have all said it was the lifters. I have been quoted $700 to replace all the lifters, is this a fair price? My other option is to replace the camshaft. I really want to give my V6 some umph and I have heard replacing the camshaft would do that. What is a fair price on replacing the camshaft? Should I just replace the lifters or replace the whole camshaft?