Easiest place to put those would be in amxx.cfg
Here is an example (you can copy and paste it in your amxx.cfg if you like)
Code:
// Ultimate Sounds Settings
streak_mode ab
kniff_mode ab
hs_mode ab
lastman_mode abc
Of course you can change the flags to whatever you want, for example, if you wanted headshots to just play the sound and not show the message, you would have hs_mode b as opposed to hs_mode ab.