help with passive attenuator values

I have a theta gen 5a with 3.5 volts and either 35 ohm (manual says)or 60ohm (wedsite says) output and wish to have attenuators installed in a pair of cary 805c. I am confused at the correct value 10k,50k,100k? Kirk at cary has says a 100k would be correct but his front ends all have high output impedance. My solid state front-end does not! As they say, measure twice and cut once. I hope someone has experience with this and will help. Also is goldpoint the kind.