Do I even need a dedicated stereo preamp?

Tell your wallet to get a job. You need speaker supplies! Lol. 
https://www.schiit.com/products/freya-f

if you’re able to stay true to this hobby, you will be completely blown away in 10 years of what you are able to accomplish.

I'll look into this for the future. But my wallet! I'm so broke right now haha

The Anthem MRX 540 gets good reviews as a 2 channle preamp, my thinking is your going to have to spend much more to get "Better" if not a side step/difference. 

Yeah I’m gonna take the other side of that.  AVRs are always big compromises as they shoehorn so many functions into one unit while designing to hit a price point, and this always comes at the expense of some of the more critical and usually pricier components like power supplies, capacitors, volume control, etc.  Then to put the delicate preamp signal through a morass of noise from all those circuits doesn’t exactly help matters.  Put it this way, in a $1900 AVR after including digital processing, video processing, streaming, a tuner, and amplification how much can be left to go toward the preamp?  Not a lot, so for all these reasons even a good budget preamp should  handily outperform the preamp section in most AVRs.  Anyway, food for thought FWIW, and best of luck adding a good stereo pre in the future. 

Do I even need a dedicated stereo preamp?

No. You don't.

Obviously you don’t NEED ONE, but would it be an improvement? It probably would be an improvement and could be a significant improvement. But you won’t know until you try. The suggestion above for the Schiit is a good one. It’s offered with IOS app remote control and has tube output, SS output and no gain output. If you get the remote option and the premium tubes is $1200 plus shipping and maybe tax. It has a return policy but I believe there is a fee. Your amp has balanced inputs but will accept single ended. I have Tekton DI’s and was actually recommended the Moab’s, but I went cheap. I have run mine with a $1500 dollar Rogue RP-1 with upgraded tubes to a cheap modded Atika 60 wpc ops amp. The DI’s are on Townsend podiums and it flipping rocks. Now I’m using a Rogue Hera balanced pre and a pair of 180 wpc Rogue M-180 Darks. And it flipping shakes the walls and sounds GREAT ! Tekton sells dealer direct and for what it is a remarkable speaker. There’s a huge fan base and a relatively large hater base. If I could afford a $15k pair of Tannoy’s or Fynes I’d by those. You could get a used SS pre that’s balanced like a Parasound or a Bryston , there are many. Or you could get a tube pre that’s not super syrupy like a Rogue. Look at Odyssey too. If your system actually improves with a pre , my GUESS is it will. The better the pre the bigger the reward. Decoupling those Tektons from the floor and proper placement will yield amazing results. Mine sound great with a pre and amp that cost $2000 total not including Tekefunken tubes and nice interconnects and power cables , but that stuff is reusable. With a $6K pre and $9k amps ( I was gifted the stuff ) it’s better , but not 7 times better. You have wine snobs and cigar snobs and stereo snobs. Don’t sweat it and enjoy the journey. Life is not the destination, it’s the journey and you’re right on track. Blessings and joy to you , Mike B. 

Need as in to make it functional, no.

Will it provide sonic improvements, almost always yes, and it grows in importance with better higher performing gear.