I have been looking around lately, and there aren't any good replacements to the GTXP. I won't buy creative (personal reasons). There are some nice cards, but nothing substantial.
for me, the best thing about the GTXP is the external breakout box. I don't know about anyone else but I dont feel like having audio cables coming out of the front of my case(ala SB Platinums), not even considering the fact that my antec case has a door which i prefer to leave closed.
Creative's had an external box for all Audigy's, no one else does it really, m-audio jsut puts everything on minijacks on backplane, or they have some firewire boxes too...