Benefit of low output moving-iron Grado ?

Hi all,
I'm considering a cartridge upgrade from a high output (5mv) Grado Sonata cartridge to a moving-iron Grado Master cartridge, either a low output (.5mv) or a high output (5mv). If I choose the low output version, I would have to drop an additional $250 on a phono card for my Exposure amp, whereas I've already got the high output phono card installed.
So my question is....
a) is there a sonic improvement in low output cartridges, or is it more a matter of taste
b) I hear a kind of "shrillness" when vocalists use an "s", and with other very high frequency sounds.... is this shrillness reduced by using a low output cartridge?
c) does Grado's moving-iron type of cartridge have properties unlike moving magnet or moving coil that might be relevant to the other questions I raised?
Thanks in advance, and I always appreciate this forum.
Thanks to both Atmasphere and Fourwinds. Atmasphere: in another universe I would be a proud owner of your equipment, from phonograph down through amplifiers. Alas, it cannot be! I am thinking of asking Acoustic Sounds (where I bought my turntable) to set up the new cartridge when the time comes. Perhaps they might be able to fiddle with the loading on my preamp at their discretion.
Fourwinds: thanks for the heads up on Dynavector... I've been meaning to look into their stuff. The 20x2 looks good, and is advertised to work with "most" MM phono stages. Is this accurate?
If others are still reading: what about these cartridges from London Decca? The "Maroon" is in my price range, and with some saving, even the "Gold". They are both 5mv output, which makes me happy. I just don't know how reliable they are. Anyone care to weigh in on London Decca vs. Dynavector vs. Grado? (p.s. NOT getting rid of my not-so-polite Vandersteens anytime soon!)
For Deccas to work well, you must get the proper arm. You're opening yourself up for problems. Stick to the Dyna, or Grado MY opinion is that although Vandersteen speakers are very good across their range, they might not be a good combination with the Grado (which has a similar "non-sparkling" presentation. I am running Vandersteen 5A's and didn't like my Grado Sonata at all...too muddy in my setup. I suspect the Dyna would be a very good match.
Advice noted. I will ask my dealer if I would need a MC preamp for the Dyna, but hopefully it is robust enough for my MM phonocard. I guess I do have to admit the "sparkle-lacking" qualities of the Vandersteens; it's funny how I lack objectivity in direct proportion to the amount of money I spend on something!
I have both Grado Sonata's, the 5mv and the .5mv versions. Same year even. I prefer the low output version hands down. So do all of my friends. The only hitch is you need a fairly high gain preamp to enjoy it.
The 0.5mv version is quieter, more dynamic, has more nuance, and is very responsive.
It's amazing what can be put on a piece of vinyl....downright spooky sometimes.