Which would be the best kind of resistors and caps to use in a DS-1 mod?
Resistors are resistors. You could use 1% tolerance resistors for more accuracy but the difference isn't going to be extreme.

As far as capacitors go, excluding electrolytic, I prefer:

ceramic < poly film < silver mica

I guess it's personal preference.

I don't believe in signatures. Ah, sh...
99% of people could not tell the difference in sound... use what you can get a hold of and can afford.