Buy some o-rings, they really do help with the bottoming out noise. Alternatively, train yourself not to bottom out.
After some coworkers complained I bought some o-rings for my brown-switch keyboard. It's much quieter although there are now other keyboards in the room that aren't quietened.
Still I like the newer quietened version, so I'm considering buying some more for my home keyboard (it is an identical model).
Yep. Kinesis Advantage plus o-rings is plenty quiet.