adding a preamp?

Hi, i have a question.
Currently i own a Marantz SA-15S1 CDP powered by a Marants PM-15S1 integrated amp, there is a tuner and a turntable hooked too. Speakers are B&W CM7.
I am thinking about gathering everything up through a pre amp that would be ultimately connected to the existing amp - in other words, getting a pre amp to gather up my sources and using the existing amp as a power amp. I am not sure if this is even makes sense or whether it`s going to work, but if it did, would it be worth the investment? Or should i tap some more and get a dedicated pre amp / power amp combo? This would practically mean getting a new system - least desired financially.

I am looking, like everybody else, for the perfect sound.

Thank you.
You already have a pre built in to the PM15S1. Why would you need another? Surely there are enough inputs for those sources on the PM15S1.
As Rodman said, your Marantz integrated amp contains a preamp (source selection/level control). Besides, to do what you're suggesting the Marantz would have to provide main amp in jacks, which it may.

Your approach has merit in that it allows you to incrementally acquire a possibly better preamp and power amp than those contained within your integrated amp.
If you intend on buying a separate amp later then getting a pre to start is fine. but if your plans are to keep the current amp, I would leave it alone and look at other components to upgrade. Don't know what other equipment you have but maybe speakers.