1: your game system should look like this:
AXP 3200 retail
cheap NF2 M/B
512MB RAM, 768 if you want
6800 vanilla
40GB 7200RPM 8MB
W2K PRO
modern case etc (lights, bs, for customer appeal, 90% of your customers will know that the comp looks cool and will think its superior)
first off, lose 2003SB SERVER. and you dont need a powerful server btw either, you are underestimating the power of that base system with added ram and maybe a UNIX environment. if you crave a little more juice go and splurge for an A64, no need for dual xeons or opterons or crap like that.
2: GET A GOOD LAN CENTER SOFTWARE + LICENSES! i cannot stress this enough. so youre going to let the user go in the machine with admin priveledges? get a lan center software and the licenses for each machine.
3: DO THE CABLING YOURSELF. dont cheap out on it, make the install look professional.
4: dont cheap out on the mice/keyboards. i would go for logitech mx510/500, or microsoft equiv. and a nice keyboard to match it. i have a logitech elite keyboard (wired).
5: choose a case with sound/headphone plugs on the front, OR integrate it into the table. this can easily be done, and will look and feel VERY good to the customer.
i end this with a question: are you going to be the guy they go to for tech support if something screws up, and will you be their upgrader in the future