I suggest freeware MediaCoder for batch converting.

Ok, ok, I personally use AVS Audio Converter 'coz I have AVS Media Bundle, but I can only suggest AVS Audio Converter if you buy AVS Media Bundle.

Freeware MediaCoder and SUPER doesn't really have an interface I would like to see, but they work fine. May be you'll need more efforts to learn them. But I think most users will be happy to use them 'coz they are very powerful and.... free .
Learn to use free software and enjoy it!