well, experience has taught me that you can't judge audio gear w/o listening to it...we all have different gear and different tastes.
I've tried all these cards, and my favorite setup is the one in my signature...discrete op-amps on the Prodigy HD2, I get the nice mellow/highly detailed and laid back sound I've been craving for since forever
*BUT* if you don't want a laid back sound, and like agressive music(many ppl do!) these two cards are very much worth a listen I'd say...on build/drivers quality the Claro Halo wins indeed(why did Asus put the crappiest DIP8 sockets you could find?!?!?!).
as for the STX/Claro Halo, I haven't owned both cards simultaneously and thoroughly run A/B comparisons...but IIRC they sound rather similar(same headphones amp, same DSP, same windows core drivers, same 24Mhz clock)...all about the details again
IMO these two cards lack a 22Mhz clock, that would allow 44.1kHz with much less jitter...but apparently their DSP doesn't support it, and whether this is audible is debatable.