The reason it's two/four is because that's the way it relates to stats.
Nade music is fine, but a client menu to switch it off would be awesome. The sound is intrusive as it lets everyone know were you are. I love this feature. As you all know, I explicitly target the nsder for knifing.
I still think the pace is too slow. I would even go as far to say that the server would be more successful with a one kill level. 2 kills with more than ten if you must.