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

And use these cables if you like detail.

Or you could use a rewire kit for the tonearm.

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.

How much of a problem the capacitance of an RCA extension would cause, if any, depends on the particular cartridge. Let us know what that is. Hopefully its manufacturer provides a recommended load capacitance range.

Also, the input capacitance of the phono stage in your AV7704 adds to the load capacitance that is seen by the cartridge. Unfortunately the documentation on the AV7704 doesn’t specify what that input capacitance is. You might want to contact Marantz and see if they can provide you with that information.

Without having a load capacitance recommendation for the particular cartridge, and without having some idea of the input capacitance of the phono stage of the AV7704, unfortunately the answer to your question has no predictability. And for all we know, depending on those variables the added capacitance of an extension might actually improve sonics, rather than compromising them.

Regards,
-- Al

Craig
Another option.
What is above the Marantz AV7704 ?
Install a wall shelf just above it. The shelf should be attached to the studs of a load bearing wall. Place you Rega on this shelf with cables feeding the Marantz below.

If the Marantz is in the middle of the rack move it to the top. .
Best to link a pic of the setup.  

Cheers Chris