[Nebby]

Google audio illusions or audio paradoxes. The brain can affect what we hear by a surprising amount.

 

[krmathis]

It affect the sound quality there and then, but I do not see how it will have any affect for later.
Just go on...
 
Consider going for higher bitrate later though, especially if you want to do some serious listening.

 

[Dev Avidon]

The bit-rate is certainly not going to affect how well the source material burns in your headphones, but it will also most certainly not be as enjoyable to listen to.  I am also of the camp that believes that you should just listen to your headphones straight out of the box.  I do believe that burn in is a real phenomena, for a variety of different reasons I have come across in designing speakers, but it's also been my experience that the bulk of the burn in is going to take place in the first few hours.  So give your phones a little time to get settled as it were, and then decide if you like the sound signature from there.