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

Blue Jeans Cables has low capacitance cables and you can order them to a custom length. Phono preamps included in a surround sound processor are usually cheapo throw ins to tick off another feature. I admit to never having tried the one in my AV7704, but an entry level phono stage should easily best it. I’m not sure where you read that the phono input of the Marantz is better than most phono preamps you can buy. That is nonsense. A Parks Puffin won’t take up much space and will sound great.

Not a dumb question and your assumption is correct.  You can use any of the other inputs but the phono input.  If you use the phono input you'll be amplifying the signal and then amplifying it again and you'll probably get a nasty noise coming out of your speakers.

https://audiokarma.org/forums/index.php?threads/how-good-is-the-marantz-phono-stage.686895/

I believe I was reading this!

That discussion was about the Marantz two channel integrateds, which are different beasts from their surround sound processors.  I didn't see any mention of the AV7704 in that thread.  My suspicion is that the phono pre in the AV7704 is not going to be as good as the ones used in their two channel integrated amps.

A couple of thoughts.

You might be getting lost in the weeds a bit with all this talk about impedance matching.  The Nagaoka cartridges are MM cartridges and they should work with most any MM phono preamp.  Unless you get something really exotic, most phono preamps should work with the Marantz.  I have a Nagaoka MP-500.

I wouldn't go crazy on a phono preamp, the Marantz is going to be a limiting factor in terms of ultimate sound quality.  You can spend a few hundred (not sure what your budget is) and get better sound quality than the built in phono pre in the Marantz, but your turntable and the Marantz are only going to take you so far in terms of sound quality.  If you want to try tubes, try one of the Pro-ject offerings, or something like the Parks Puffin if you want to go solid state.  I think anything beyond that might be a waste of money for your current setup.

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.

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.