I'm no expert, I tried to Google without much luck for a comparison.
I do remember a video by a successful disc jockey who used M-Audio speakers (I think AV40's) and an M-Audio sound card.
I have M-Audio AV40 speakers. It's interesting how often a cheaper set of speakers sounds roughly the same as my speakers but how much different they are for quality audio. I absolutely LOVE my speakers. I can listen to audio without my computer by using the front input connected to my MP3 player. I can't remember if it's included but the wire is a "Male-to-Male 3.5mm Stereo Audio" cable.
Without more information I'd recommend one of the M-Audio cards. The following is probably the link you want:
http://www.m-audio.com/index.php?do=products.family&ID=PCIinterfaces
All cards are PCI. PCIe support isn't a big deal. Eventually PCI will be dropped. Audio cards don't need the extra bandwidth rather it just makes sense for all motherboards to go with only PCIe to save money. It will be many years until PCI disappears completely from motherboards.
Many people who get Pro audio boards also get the front component but that's if you need access frequently but I'm no expert anyway.
ASUS has only one "pro" board and that's for a Home Theater setup not audio processing in the professional sense.
Good luck.