You could, in fact you SHOULD, use that standalone phono preamp as an extender for that additional length. What that will do is amplify (and provide RIAA equalization) to that low-level phono cartridge signal so it can carry over a greater distance.
But instead of feeding it into your Denon's phono input you'll need to feed it into an "Aux", or high level, input on your Denon. The signal has already been boosted to what the Denon's internal phono amp would do. It'll be over-driven otherwise.