Just like the ordinary P4 PC - resistor mod (lower fan rpm) isn't a good idea, it can get hot as hell, quieter and more efficient heatsinks are way to go, same with liquid cooling (good one is too expensive to use in lindbergh though)
found this info last year at arcade otaku: source: http://forum.arcadeotaku.com/viewtopic.php?f=26&t=26978
Yep ive got one and yep its loud as hell. Everyone always says to never change the fans but in the end its basically just a 2005 pc. I was gonna look at replacing the fans with silent ones at some stage myself but haven't got around to it yet. Ill post back if I ever do it and let you know how It goes
The loud case fans really aren't needed. You have to remember these systems are shoved into a confined arcade cabinet which is why those case fans are there.