Interconnect Length

What kind of cart. are you going to try to use? With a MM cart. the capacitance of 20' will probably kill you. With a MC I'm guessing that only a balanced connection has a chance of working out.

In a phono cable 3 ft is best for sound.

Are you connecting the phono cartridge directly to the phono stage of the pre-amp, or are you connecting to the output of a seperate phone stage?

If the former I agree with the comment about 3ft. If the latter you could stretch it out a bit, but still wouldn't strech it out to 20ft. I keep all of my IC's no longer than 10 ft and use 3 ft when possible.

THanks for helping - I don't even know what cartdrige I would use - I have not touched nor consider getting a turntable since I am 14 years old... I am out of the loop. 
All I know is that I would use RCAs into my integrated, and I would place the turntable on a dedicated stand, to avoid all vibrations from walking and playing the sub on hardwood floor.
Maybe I could place it on the left corner of my room... (see my room in virtual systems).