i'm actually using those sound absorption mats...but they're pretty much useless...there's no significant difference with the sound output from case...total waste of $20...i only kept them b/c i don't want to leave behind a sticky mess when i remove them...
better idea would be to invest in quieter fans...which is what i did...
P4C 2.8ghz o/c'ed to 3.36ghz
Asus P4C800 Deluxe mobo
2 x 512mb Kingston HyperX pc4000 DDR
nVidia GeForce 6800
Sound Blaster Audigy 2 ZS Gamer
160GB 7200rpm SATA Seagate
74GB 10000rpm Western Digital Raptor
ATI TV Wonder Pro