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

You need a very well shielded phono rca cable from your tt to your phono input. There must be a third line just for ground (wire). As i said it's a bad idea to use unbalanced phono cable for longer than 1,5 meters (even this is too much). What is your cartridge? 

You can try external phono stage with short cable from tt to this stage and longer cable from phono stage to your line input. 

Ok I think we are onto something.

First, the noise didn’t change when I moved the Marantz around. Second, I have a second Marantz (same one) that I tried and the noise was exactly the same.

Third, even though the TT was turned off I decided to remove the phono cables extensions and it got rid of the hum. I’m assuming it got rid of the ground hum since there is no ground wire coming from a Rega table to connect. 
HOWEVER, even though the hum is gone, in the phono selection of my Marantz when I crank it up there is a smooth hiss like the ocean. Is this inherent in all phono or will an external preamp that is of higher quality get rid of this?

Finally, the rumble problem is still there but that’s different issue. 
Also,I don’t have an external phono preamp to try at the moment. I will be ordering one soon though. 

Guys,
I may have figured it out and I would like to get your opinion. The P3 mass is 11 g. My Nagoaka MP-110 cartridge is 6.5 g with only a 6 for dynamic compliance. Using an online calculator this puts the resonant frequency at a 15-16 Hz!I believe it’s supposed to be around 10 Hz correct?
Do you agree this is most likely my problem?

It appears that the Rega P3 is normally fitted with a Rega RB300 tonearm, which according to the listing at Vinylengine.com has an effective mass of 11.5 grams. Also, since the cartridge is made in Japan its dynamic compliance is probably specified on the basis of 100 Hz, rather than on the 10 Hz basis that is usually used by the calculators, such as this one. I would expect that its compliance at 10 Hz is **probably** in the rough vicinity of 10 or so.

Plugging a compliance of 10 into that calculator in combination with a tonearm effective mass + cartridge weight of 11.5 + 6.5 = 18 grams results in a calculated resonant frequency of 11.86 Hz, which is within the 8 to 12 Hz range that is often considered to be ideal.

But note the word "probably" in my statement. It’s hard to say for sure.

Good luck. Regards,
-- Al