Hi folks, I'm new here, and I'm looking for some upgrade advice...

My current setup:

laptop USB --> Corda Symphony 2 --> AKG 702 (All standard stock wiring).  I use the high resistance, high gain, crossfeed setting. Most music sounds pretty good, but with some poor mp3 rips there's background buzzing. I'm thinking about upgrading some of my pre-headphone equipment (not getting rid of my 702s, they probably the most comfortable headphones at the price range, and i don't think 2nd hand headphones are that appealing anyway, they've been around somebody else's EAR for extended amounts of time)

1. I will buy a new desktop soon, and will probalby use a co-axial/SPDIF input to my Symphony. Should i just go ahead and use the one on the motherboard, or is a discreet soundcard recommended?

2. (I obviously can't tell), but from some of the online reviews I've read, the "DAC" part of the Symphony is merely "okay" while the  "Amplifier" bit really shines. I have also heard that my AKG 702s (whch I am really satisfied with compared to my previous HD595s) are "annoying to drive" and "fickel with equipment."

I'm interested in either the Grace M903 or the Benchmark Pre DAC. Are the integrated amps on the units good with my 702s?

3. Any suggestions for wiring upgrades? I've heard the Oyaide wires for my 702, they cost around 2300 NT dollars here in Taiwan (about 70 dolalrs US), and honestly, Ican't tell the difference between the stock wiring.