New RSA predator owner with questions/concerns

Hello people,

I am now a proud owner of an RSA predator amp/dac! I love the way the amp sounds now and I know that it will keep sounding better as I burn it it. I do have some questions and concerns about the DAC section of the amp. When using it with my macbook pro, I was surprised with the fact that changing the volume on my computer while the dac is functioning actually changes the volume on the amp. I own other soundcards/DAC's, and none of them do that. Once connected to my mac, the devices bypass the software volume control and use the hardware instead. On the other hand, the predator's volume can be changed from the computer and from the volume knob on the device itself. Also, the DAC section sounds horrible with Itunes and all media/music players I've tried. However, the music on Grooveshark sounds very good, so I am really confused about why the DAC section sounds terrible with itunes, quicktime, vlc, etc... but sounds great with an online music player such as Grooveshark. I really hope there is a quick fix to this because the last thing I'd want to do is send it back for inspection/replacement. When I say terrible, I mean worse than plugging my headphones in my mac's headphone output; Which for those of you who own a mac, know that it's horrible sounding. 

Thanks for your support!

There were no problems with the settings in the audio midi setup. I am very disappointed with the DAC sound quality. There's definitely something wrong here...

I'll take that back, some songs on grooveshark sound ok others sound just like itunes. When I play songs in itunes, and press play/pause, you can here a kind of echo or a kind of reverb that sounds very "electronic". I have just tested it on a windows computer and it sounds great, so there has to be something wrong with my computer. Any ideas what that might be?

At least it's good that I isolated the issue. Maybe someone who owns a macbook pro can suggest what to do?

Nope, it's something much more problematic than that! It's really starting to frustrate me. I really see no reason why it works fine on a windows pc but not on my mac. Maybe I should try it on someone else's mac...

This is so random. When using the Decibel music player, the sound is fine compared to when using itunes, quicktime, vlc and any other media player. I guess my predator is very picky with its choice of media players. Can anyone explain to me why I am experiencing bad sound quality with such players. Youtube videos sound great too... This is very weird and irritating!

Sounds fine when using quicktime 7, but terrible when using the old quicktime pro. How do i run a check on the software in disk utility?

That didn't solve the problem Jamato. This is really getting on my nerves and I need to find a solution to this problem somehow...