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).

Is it possible to mount your TV on the wall? That way, turntable would fit on the component stand.