The Single most important component in a preamplifier if not going with a stepped attenuator go with as high quality potentiometer as you can afford - the TKD IMO is superior to any Alps one - here is a 100K Audio taper one
http://www.partsconnexion.com/tkd_70897.html
Best of luck
Peter
http://www.partsconnexion.com/tkd_70897.html
Best of luck
Peter