[as.we.proceed]

You should reconsider. While the 780 performs good with well recorded albums, they are nearly unbearable for albums that are recorded too bright and this happens quite often with the genre.
 
Look at the newly released XB800 if you want a sony.

 

[Hoagie]

I did not realize that the XB700 had been discontinued.  I checked on the J&R site and discovered that there is now a XB800 and XB600.  I assume these are replacements.  I wonder if there is any real difference.  As to the OP's question, I have tried both the XB 700 and the 780.  I run both as semi portable (coffee shop, library etc.) from my Ipod with a line out and portable amp.  I appreciate different sound signitures, but over all I prefer the 780's.  To my untrained ears they have the more defined bass and also more bass impact.  
 
I do think both benefit greatly with the use of a line out and amp with the Ipod.  The actual amp makes less of a difference.  The e11 does a very good job. 

 

[fabio-fi]

The latest XB models from sony aren't that great from what i know. 

 

[Roller]

Quote:

The latest XB models from sony aren't that great from what i know. 

 
Reports do seem to indicate that.