If the lack of sounds frustrates you, I recommend listening to music while playing Minecraft. Or even chatting with friends on some voice chat server. I generally do both at the same time, so the lack of minecraft sound effects doesn't really bother me. Also, Matmos quickly became annoying, and I often found myself disabling it completely after a short while.
Yeah, MAtmos can sound quite cool when you first start out, but maybe the amplitude ratio of MAtmos to Minecraft sounds isn't really that good.
I know IC2 adds quite a few sounds to their machines, and Advanced Machines use the same.
MystCraft adds a few teleportation sounds.
That's most mod sounds I ever hear on FTB, really.