passive line level volume control

Can someone recommend an inexpensive passive type line level volume attenuator for a bi-amp application? I'm wanting to bi-amp my planned esl and I have two amps and one preamp. Neither amp has a gain control and the preamp doesnt have separate gain controls so I need some way to balance things out.

I'm thinking I don't need a line level amp, just a pot in the line to crank one amp down. Any suggestions to a newbie with no electronics experience?