We need 5k ohm digital potentiometers, more of those amplifier kits, and an i2c multiplexer to route the signal.  The other chips will be useful when we want to make every thing smaller.  The steps are limited but with the right configuration of resistors, I should be able to get the range we want.

• digital potentiometer: http://www.mouser.com/ProductDetail/Microchip-Technology/MCP4017T-502E-LT/?qs=%2fsslhGPpiORmi5j1%2fj4XKWyG27pODiC2w736XYhYJGU%3d
• multiplexer: http://focus.ti.com/docs/prod/folders/print/pca9548a.html
• IC adapter.  We will probably need one for the multiplexer: http://www.proto-advantage.com/(Talked to these guys on the phone when looking for a mount for the tiny chips.  They had something close but not quite the right form factor.)

I am going to have to double check the sizes to make sure they are all workable.  There may also through pin versions of the circuits.  Surface mounting isn’t too hard but it does mean that you need a PCB.