Mordante, your best option in this case is to replace the junction box with one for XLR cables, and run everything balanced. The advantage of doing this is that the cables will have less overall effect on the sound- they will be more neutral.
How to accomodate a balanced only phono stage ?
I've got my eye on an expensive Phono stage that only accepts balanced inputs - from my experience about 99.9% of the tables out there are single ended only. Is there a cost effective way to convert an single ended turntable to supply a balanced input of a phono stage (without compromising the signal)? thanks for any input.