Best Way for my TT to reach my Pre-Amp!?

The Marantz is a home theater processor and has a lot of electronics stuffed into one box.  It's good at a lot of things, but not great at anything including two channel music reproduction.  I have a separate two channel preamp (a Modwright LS100) that I use for two channel listening.  It lets more of the music through (I don't know how better to describe it) than the Marantz.  It has a home theater bypass circuit so I can share my amps and front channels with the Marantz when I'm using it for home theater.  The Marantz isn't bad by any measure, but it's a compromise when used for two channel music.

First, I love the analogies of Miller Carbon! It really paints the picture!

Also Greg, that makes total sense the way you explained it! Thank you!

Ok, so is there something you recommend that will act as a phono preamp that can also bipass the Marantz and go straight to my Atoll Amp being shared with the Marantz? 
I can’t stress enough the difference between the Atoll and the Anthem. How can a $4500 A5 Anthem sound like complete garbage next to the $2000 Atoll? It’s flat and dead where the Atoll is like sitting in the pit of an orchestra. 

Craig,

You could try things in steps and see what you think of the sound for yourself.  If you like what you're hearing with what you already have, you don't necessarily need to go down a rabbit hole.

First, get some Blue Jeans cables that are of a length that would allow you to connect your turntable to the Marantz.  If you get a phono pre you're going to need another set of cables anyways.  If it sounds good to you, you're done.

If you'd like to take it to the next level, then get a phono preamp and try it in place of the phono stage in the Marantz.   If it sounds good to you, you're done.

If you want to bypass the Marantz and have a cleaner route (less distortion from the Marantz) from the turntable to your speakers, then your next step is to get a 2 channel line stage or preamp, preferably one with home theater bypass so that you can share your front speakers and amp. 

A line stage doesn't have a phono stage and would be all you need if you've already bought a separate phono preamp.  A two channel preamp will typically include a phono stage.  Depending on the quality of the preamp, the included phono stage may be pretty decent.

I can custom made phono cable for you. If you don’t like it, send it back to me and I will give you money back. ventusaudio.com

Consider iFi iPhono as a phono preamp. It has settings for capacitance and various settings for the equalization. I like mine set at 100pF and use their proprietary eRIAA settings for equalization. By playing with the settings you will be able to hear what you like. 
Also, as far as I understand, capacitance does not matter if you use a Moving Coil(MC) cartridge. The iFi has various settings for loading impedance for an MC cartridge. Just keep the cable length from your Rega to the iFi short. Another good thing about this preamp is its size - you can hide it behind your Rega. 
Hope this helps.