I'd say the mod.
Hardware can always be upgraded (or downgraded) to suit the application.
I'd rather see a really awesome looking PIII firewall or printserver box than a top-notch gaming rig in a beige box that someone has "modded" with only a sticker.
Your mod will still be amazingly cool three years later, where as your graphics card and liquid-cooled USB ports will be old news.
Just my two cents.

