Help me upgrade my beginner system!

From about 60Hz up, your speakers will more than hold their own with just about anything. But your subwoofer is an entry level unit. I would look at a REL or a pair of SVS 3000s. As for your cartridge, the stylus may be pristine, but at 50 years old, the rubber suspension of the stylus has to be hard as a rock. I would look at a high-output moving coil from Hana. If you don't listen to much vinyl, then maybe consider a DAC. Just make sure you can return it if it doesn't change things much. You have a great power conditioner, so leave that alone. I would next turn to your room. Nothing - no other component upgrade will make as much improvement to your listening. For $2500, I'd go with 2 SVS Micro 3000s and room treatment before anything else.

also, I would not say it's a beginner system, but it depends on where you look at it from. It makes you sound like you don't know what you are doing when you clearly do. If you think your weakness is the lack of a DAC, that's what you could try first. 

These are all great suggestions, however given where you are right now I too, lean towards replacing your speakers. 

You may want to consider Elac Vela Floorstanding 407 or 408. 

https://www.elac.com/category/floorstanding-speakers/vela-fs408/

You would problably get the best investment value as it has a very good frequency response (Larger Sound Stage) for the money.

@dvujovic j Your PeachTree Nova is OK not great. I had the PeachTree NOVA 150 for a few years.

I suggest you take a chance and buy the Peachtree GAN1 and the BluesNode streamer for sub integration, analog input, and MAYBE volume. I am not sure about volume.

Trade in the NOVA 300 for the GAN1.

GaN 1 | Peachtree Audio

Now this will be better than what you currently have. However, if you are willing to lose the warranty. Send in the unit to Ric Shultz at TweakAudio.com and let him do the mods that he did to my unit (I was the Guinea pig for these mods).

Digital amp mods (tweakaudio.com)

This unit is so good now that I sold $7K of gear that became redundant.

In the past, I spent around $30K to drive my RAAL SR1a headphones using 2-channel gear. The modded GAN1 is better than that on my headphones and comparable to the the 2-channel gear on my 2-channel speakers.

Since you already have a NOVA 300 this trade-in and mod is something economical.

BTW - In the PeachTree hierarchy, in a scale of 1-to-10. My old Nova 150 was a 1/10 and the GAN1 is a 10/10.

BTW2 - I use a Lumin X1 DAC as a SPDIF streamer to the GAN1 via fibre optic input to the X1. This is a $15K streamer and likely much better than the Bluesnode streamer. However, the NODE give you sub integration and analog input. Both of which I lack on my X1 streamer.

BTW3 - I think what I am suggesting is similar to Mark Levinson’s new company and product.

Maria Amplifiers – Daniel Hertz SA

I just saw this online.

Peachtree GAN-1 unboxing & video review | Darko.Audio

Have not watched it but the stock unit is not as good as what I have. The difference is rather big.