How to do room acoustics correction the easy way.

I have been researching all the methods to do room acoustics correction with an existing system with a existing DAC.  What I want  is a device that connects between my stereo preamp and stereo amp that will do the work.  I want it great, but I want it simple.  I want all my sources to go through the “box”. 

Am i missing something obvious, or is that not how this stuff works?

Your feedback is greatly appreciated....