I've also been thinking about doing something similar to this.
Couldn't you also put a 3p2t switch on the output of the Quickie, and then have one of the outputs of the switch go to the Quicksand and the other go to the RCA jacks?
Using the attached picture, I think it'd look something like:
Row 1 = Left
Row 2 = Ground
Row 3 = Right
Column A = Output to RCA
Column B = Input
Column C = Output to Quicksand
I think you would:
1. a) Detach 2.2µF output caps and 475KΩ resistors from left and right RCAs;
1. b) black ground wire from pot to right RCA -- detach from right RCA;
1. c) wire Quickie's left and right 2.2µF output caps directly to 1B and 3B, respectively; black ground out from pot goes to 2B;
1. d) put one 475KΩ resistior between 1B and 2B, put the other between 3B and 2B on 3p2t switch
1. e) wire 1A, 3A to center pin of left and right RCAs respectively
1. f) wire 2A to ground tab of right RCA
1. g) wire 1C, 2C, 3C to left, ground, and right, respectively, on Quicksand board.
OR
2. a) Detach 2.2µF caps from RCAs, keep 475KΩ resistors in place;
2. b) same as above;
2. c) same as above;
2. d) another set of 475KΩ resistors go between 1C, 2C, and 3C, 2C;
2. e) same as above;
2. f) same as above;
2. g) same as above.
As I see it, option 1 doesn't require any additional resistors, but might be harder to wire; option 2 requires an extra set of resistors, but might be easier to wire.
Is this correct?