There is no option to choose the audio quality when you import a wav file and it is converted to .cts format.

Once you export a video the audio quality varies by the output options. For example .wmv output formats use profiles which have the audo quality set in them. 

To give you an idea, here are some example audio wmv outputs.

Broadband (384kbps) = 32kbs Audio

Broadband (764kbps) = 64kbs Audio

File Archive Options = 128kbs Audio