Pros: ORGANIC SWEET NATURAL SOUND
i agree with pretty much everything skylab has written about the isabella,however, in my opinion-
i think the isabella is a real bargain @ 6k. at this past 2010 canjam that i attended,i heard a 10k amp
plugged into a 14k cd player = 24k in which i would not trade my isabella for,no way!
just like many here on head-fi call the sony r-10 s "the king of dynamic headphones" i consider the isabella pre-amp to be the king of tonality!
in addition to its wonderfull rich tone,the isabella is the most organic and natural sound i have heard from any piece of audio i have owned,or have listened to from the countless meets that i have attended since 2005! my ears are highly sensitive,and fatigue very easily,but not with the isabella or any of the rwa products that i own.
another aspect of red wine products,including the isabella is how forgiving it is with poorly recorded material! isnt it amazing,how you go to meets,and everyone has "audiophile recordings" playing through there rigs?and then you drop in a cd that you happen to like,but not recorded well,into that uber expensive set,and it sounds like crap?
the isabella makes the most out bad recordings,while not giving up anything!
on audiophile recordings,the isabella is just heavenly,as if the pre-amp just dissapears poof.
and all that is left is pure magic