I am told that in studies done on each of the filters and the AC is about the best even compared to the Mobil 1 and K&N. I am personally using the Amsoil, but only because I put their oil in for the first time and wanted a filter that would match the change cycle.
I know it wasn't one of the three the original poster asked about, but I did confirm with AMSOIL techline that the EAO32, one of the new AMSOIL Ea Oil Filters which are rated for 25,000 miles or one year of use, is the correct filter for the LS1, LS2 and LS6 motors. :cheers
Thanks for all of the suggestions. I used K&N in my Contour SVT, and my brother is also suggesting that I use the Amsoil oil and filter - I think he's a preferred customer, so the price would be good - but I've almost decided to go with AC-Delco's UltraGuard Gold. Just a GM thing, I guess.
I've even decided that I might not go with a Borla Cat-Back - will probably go with Corsa's Sport system (PN 14189) because it's offered for sale at the dealership. I'll have to look at both systems a little closer before I actually decide for sure.