[gazeds]

Is there much differance in sound quality using a full-size headphone amp rather than a portable amp with an ipod or iphone, and grado rs2i's

 

[legcramp]

In general, you pay for the portability. A full-size amp will perform better than the portable amp that cost the same price.
 
But then there is also the synergy between the headphones / amps that come into play.

 

[Yaozilla]

Yes, you will notice a huge difference.

 

[metalh3ad]

Night and day difference. Yes. 
 
You get the most of them with full size ones.