It all comes down to sound preference and budget. Almost all mufflers sound good with an X pipe, a lot sound good with an h pipe, some shouldn't be paired with an h pipe or the car will sound like a burly pickup.
My two personal preferences, taking into account my modest budget, are as follows:
MAC Shorty headers
MAC Off Road H Pipe
Flowmaster 50 Series Mufflers (aka 3 Chamber or Force II cat-back)
MAC Shorty headers
MAC Off Road X Pipe
MAC Flowpath Cat-Back
Others sound great, including Borla, Bassani and Spintech, but you will pay a premium for those. I am not a fan of Magnaflow, though many on this board are. I am also not a fan of SLP on a 5.0...
Search this forum, and hit up youtube and search the different combos...