My brother has a Hercules Game Theater XP with the breakout box, and my friend just bought a Soundblaster Audigy Platinum EX with the external breakout box for his new computer. Both cards sound great, but the Audigy has more connectivity options, a remote control, IEEE1394 firewire port, and 24 bit hardware audio codec, plus a very extensive software bundle for music and audio creation. On the other hand, the Audigy is the better part of $250 versus probably less than half for the GTXP.
Personally, price no object I'd get the Audigy Platinum EX, but I'm not sure if someone really needs its capabilities. The Game Theater XP is a great card, and I have no qualms recommending it over the Audigy. Low CPU usage, 4 USB ports, optical and coax digital in/out, it's good enough for now...