you can try pming skypainter-- i believe he is running a i3, 4-way setup like what you're thinking about-- it's been a while since i've seen him, so i don't remember his whole setup..
but first things first, if you have any serious interest in competing, a carpc might be completely out of bounds. i haven't read the iasca rules for a long time, but from what i remember form redgtivr6's posts(she used to compete, and for a while seriously looked into building a carpc devoted to it), the rules state that the setup essenstially needs to be dummy proof, info needs to come straight off the cd, and can't be pre-recorded,-- ie, the tester inserts the test disk, presses play, and it works only off the disk.
i've also read more than once that audio comps are heavily weighted by the gear installed-- if say kicker is sponsoring the show and you're running all alpine gear, there can be deductions for it, er, maybe it's not brand specific, but i've seen mention of people complaining that if they don't have such-and-such gear installed, they get points taken off tehir overall score because of that-- so much so, that many competitors openly state they keep dummy gear installed just to maintain the points... i've also read that a newer category in iasca comps is related to how clean the install is, so a run-of-the-mill system is going to get lower points than a fully fiber glassed/wire-tucked install, even if the more basic system clearly sounds better..
otherwise, i stay pretty much out of the loop of available sound cards... i use a esi gigaport hd-- the major downside is that it absolutely requires preamps to get anything more then a whisper in output level, but the upside for me is that allowed me to use the cl-rlc preamps w/ volume control, so i could migrate that feature off the pc.. i just got a email recently that there's a new version, no idea if the same traits apply.. but the card meets the needs of 8 outputs at least..