Well...this is of course a highly opinionated subject. Music to one person is noise to the next, ya know? I've personally tried a bunch of mufflers and my favorites at the moment for an X pipe are Magnaflow and MAC. I haven't owned Spintechs yet but i've heard a few clips and they sound great too.
What do you like more of, rumbley or raspy? An X pipe is going to make most mufflers sound more raspy, so a muffler like Flowmaster that's usually rumbly is going to give you a different kind of sound...not necessarily bad, but different. The clips i've heard of Magnaflows with an H weren't for me, but i love them with an X so it's all in what you like.
I'd do a search here and online for 5.0 exhaust clips and just narrow it down to something you like the sound of.