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

 my isabellina hpa is the 2nd hpa that i have purchased from vinnie! the 1st unit i upgraded to isabella pre-amp which i use with rwa 30.2 power amp and my harbeth hlp3-es2 speakers (system) what makes the isabellina hpa better than "ALL" previous amplification that i have owned in the past is very simple, and here are the ingredients 1-discrete circuitry (no opamps) 2-high current sealed lead acid batterys 3-highest quality parts inside 4-highest quality of cabling inside(yes premium cabling does make a difference) 5-16bit r2r nos dac (giving a very organic & natural sound)(not a washed out sound like most upsampled dacs ive heard) the above mentioned portrays richness in tone unlike any other the sla batterys provide a dead black background unlike anything out there the bass is tight,deep and full the highs are all there,and the mids "WOW" you have to hear them to believe it! ok here is the most important feature for me! my isabellina hpa as well as all my rwa products i own is the most non-fatiguing listening to my ears! it doesnt matter how loud or soft i play my music. i can listen for hours & hours & hours!!! no fatigue for me!