With no mention of budget, it's impossible to make an specific recommendations.
That said, I'd start with the lowest hanging fruit and one significant upgrade to your existing turntable that won't cost you anything more than a bit of your time: remove the built-in preamp. Doing so will make an audible improvement in sound quality. That built-in preamp has two little LC filters that remain in the circuit when you throw the switch to bypass the internal preamp. These filters are intended to block any noise coming from the USB circuitry. They do, but they also dull the sound. Removing the built-in preamp removes both the source of the noise, and the filter, which then becomes unnecessary. There are videos online that show how to remove the internal preamp. It's not rocket science. All it requires is basic soldering skills and the ability to follow instructions.
Next up, I'd recap your Dynaco A25 speakers. Those are actually some well respected and pretty decent sounding vintage speakers that are a good match for your Marantz 2230 receiver. Recapping the A25 crossovers is easy, getting at them is the hard part. They only have a single 5uF capacitor per speaker, but getting the grills off and removing the woofer is the tricky part. Dynaco used some black tar like substance to seal the woofers that makes it challenging to get the woofers out of the cabinets to get at the crossovers. Take your time and work slowly is the best advice. As far as the crossover is concerned, any decent 5.0 or 5.1uF film cap will be an upgrade. If I was going to the trouble, I'd go with at least a ClarityCap PX ($5.55 each from Madisound - great cap for the money), better still a Sonicap Gen 1 ($13.79 each from Sonic Craft). Again this is an upgrade that will cost you more in time than money.
Then, I'd look into upgrading either your cartridge, or stylus. There are better styli that will fit your existing cartridge. Check the offerings at LPGear. There is a 0.3 x 0.7 mil Audio Technica ATN95EX stylus available that is supposed to be a noticeable improvement over the 0.4 x 0.7 mil ATN95E stylus that originally came on your turntable (Note: rumor is current ATN95E styli are also 0.3 x 0.7 elliptical, but you said you bought your turntable a couple years ago, so the ATN45EX should be an upgrade). That's just one option. LPGear also offers a 0.3 x 0.7 mil elliptical with a carbon fiber cantilever at a reasonable price. They also offer their own house brand VividLine, Shibata and line contact styli for the AT95E. These used to be great bargains, but they have raised the price to where they are no longer cost competitive. The chief reason is all the styli in the newer VM95 line will also work on the AT95E. You can get genuine Audio Technica styli in advanced profiles for comparable, or less, than what LPGear is charging for their house brand products.
Lots of options in replacement styli, but of course, there is no reason to limit yourself to just styli. If your budget permits, you could consider a new cartridge from Nagaoka or Audio Technica, or a vintage cartridge like a Shure M91, M95 or V15 Type III with a replacement stylus from JICO/LPGear. It really depends on your budget.
Hey folks
