Digital BW, The Print

I've been "away" - but not in the "big house" :-), and now
investigating a 2400 (primarily for B/W) to add to my 4000 and 2200
stable for 17"x and 13"x salon prints.

Assuming OEM (stock) inks & machines in all cases; would some of you
good folks give a judgment of the improvement of the K3 inkset over
the earlier (4000) UltraChrome formula, for both B/W and color
applications?

If "1" is hardly noticeable and "10" is "amazing, can't believe it -
goosebumps",  where would K3 fall on the scale?  Any comments,
perspectives and recommendations would be much appreciated. 

I've of course read the Epson K3 "line"; now I would appreciate
hearing what the pros have found to be "real"!

Thanks,   Gordon