Thoughts on upgrading TT signal chain

How old is the Bronze cartridge? How does the stylus look? Is it worn out? Before getting a step up Tranny you should look into those questions. If the stylus is worn then you can get a new one if the cartridge is not too old. If not, why not look for a good MM or MI (moving iron)cartridge. This may be the ticket to better sound. 

As to the phono preamp, It is as important as the TT & arm and should not be overlooked. I don't know how good the one in the Nova is but I suspect it is the weak spot of the vinyl system. I do NOT like step up trannies unless absolutely necessary. Others will disagree. I'd put my $$$ into a good phono preamp first rather than tranny. But again, the stylus may be the problem. Get a jewelers loupe or USB microscope and look at it . 

Any suggestions on particularly quiet pre amps?  I've looked at the stylus and don't see wear on the diamond.  However, where the cantilever comes through the o-ring surround doesn't seem perfectly seated.  I haven't been able to source any photos to compare to though. Thanks for the input.

How are your cartridge balance/alignment skills? All must be right for any cartridge, the existing one may be worn, or poorly balanced aligned.

I suggest you start with a new moderately priced MM cartridge, advanced stylus shape: SAS, ML, MR, Shibata ....

https://www.audio-technica.com/en-us/cartridges/type/moving-magnet/vm540ml-h

Your arm has a removable headshell, that makes things easy to have different cartridges pre-mounted, switch: existing; new stereo; new mono; new MC (from SUT thru your Peachtree MM or from a separate MC phono eq).

This will tell you for certain how much you do/don’t like your Peachtree’s MM Phono Eq.

IF you get a MC, and boost it via a Step Up Transformer (SUT), you will still be using the same Peachtree built-in MM Phono EQ. That is what I/we do when we have a MM Phono stage we love.

IF you are not wild about the sound of a new MM thru Peachtree’s MM, then I suggest step two is a separate Phono stage with both MM and MC, (preferably the ability to change MC settings). Now the MM you bought or future MC go to Peachtree Line In, skipping it’s Phono Stage.

This of course opens the possibility to try Tube Phono as well as SS Phono.

ANY Phono Stage, I strongly advise having a return option, it's not easy getting one you love.

After you get a successful Phono Stage, then you can move on to a MC cartridge when ready. And, if you have Mono LP’s, I learned here how much better Mono LP’s sound thru a true Mono Cartridge, I chose Grado Elliptical stylus shape for Mono, advanced shape for both MM Stereo and MC Stereo.

Get properly hooked, even if hard work, you won’t regret it!

Agreed. Start with a known quantity. The AT VM540 is very good and inexpensive. It'll make a fine backup cartridge in due course. 

Very reasonable advice, thank you very much. I like the idea of a clean slate cartridge but it is complicated by the fact that a replacement stylus for the bronze is nearly the same price.  I imagine a cartridge body is less likely to be damaged than a stylus, but what exactly can go wrong with them?  I guess it's like you're saying...a known value is the starting point. The stats on the AT VM540 seem similar to the bronze.

Also, can you recommend low noise phono pre's and retailers that have a try it out policy?