You can add however many sounds you want, for every, single achievement sound in the program, yes. I.e. the AvP voice pack I have, has 35 unique sounds for the per-kill feature alone. And then you can add 10 for MAX takedowns, 10 for each level of killstreaks and so on. The only downside is that it is kind of tedious to add them one by one. And afaik there's no quick way of adding a whole bunch.