Hello again C,
I'd get Vishay RN55D resistors (Mouser is a good source) for the Sweetest Whispers, and potentially get some empty Goldpoint switches to replace the Lorlins (one 4P3T-1D and two 1P12T-1D).
In the Extended model, there are four 237 Ohm resistors on the active loads that are somewhat important, using RN55D's here is a good idea too.
There are some series input resistors that feed the attenuators of various impedances, I'd use what's in the kit to see which values you like.
The output coupling capacitors are another nice place to invest in some good parts.
There are also some small 0.22uF capacitors in the power supply, rated at 250V. You won't have a ton of room to put exotic parts here, but the 250V film capacitors from Parts Express fit nicely.
I hope this is helpful, you could certainly put nice parts everywhere in the circuit, but these should be the ones that help the most.
-PB
