Next upgrade to an entry-level system?

Get into room acoustics early

parkergetdean and ghdprentice are correct.

The best (and proper IMO) way to improve an entry level system is to upgrade speakers first. However, you want to upgrade them to a level that the rest of the system is obviously holding them back.....then as you upgrade everything else, they will sound even better. Buy used for sure as you upgrade

Works rather well in going from entry level, to low fi, to mid fi, to hi fi; I've upgraded several times on my way up over the last 

Probably a miniDSP on your subwoofer honestly.  Usually you end up leaving it's level too low due to room modes.  Find them, clip them with the EQ and you can find your way to much fuller sound. 

Hello I suggest Harbeth P3 ESR speaker upgrade of any iteration even tho they have become so $$.Everything will sound better right away. Then let yourself find a more sophisticated amp for them you won't need much power. Avoid Type D, perhaps get into tubes that would be fun.

Best JS

As others have said, the phono preamp is a good call for your next step.  I think you should spend time listening to and reading about equipment.  Find a local high-end hi-fi shop and understand what brands are available.  

You don’t mention a budget.  You’re better off buying used, high-quality components piece-by-piece than run-of-the-mill stuff.  For <$5k, I built you a serious system that you could live with for a very long time and likely be happy: 

Audible Illusions 3A Preamp -  $1300 (This is a great Class A, dual-mono preamp) includes a phono section.

Jeff Rowland 112 Amp             $2399 150‑watt‑per‑channel stereo power amplifier, machined from a solid block of aluminum.  Made in USA

Moon  LP5.3 phonostage          $721 (widely regarded as one of the best sub‑$2k phono stages ever) - You don’t need this, the preamp includes a phono section. 

ITC-1 Speaker                          $495 (a boutique, engineering‑driven design with an external equalizer and unusually advanced crossover)

GRAND TOTAL                        $4915 

You already have a turntable so, I excluded it.  Use the leftover $85 to build your own speaker cable. 

(An alternate honorable mention speaker is the classic Dahlquist DQ 10 - but it went over my suggested $5k budget @ $699)

Audible Illusions 3A Preamp -$1300 https://tmraudio.com/fresh-arrivals/audible-illusions-modulus-3a-stereo-tube-preamplifier-mm-mc-phono/

Jeff Rowland Amp https://tmraudio.com/fresh-arrivals/jeff-rowland-design-model-112-stereo-power-amplifier/ $2399

Moon by Simaudio LP5.3 phono preamp $721 - https://tmraudio.com/fresh-arrivals/moon-by-simaudio-lp5-3-mm-mc-phono-preamplifier/

ITC-1 Speaker ($495) - Very Efficient w/killer sound  sound https://www.ebay.com/itm/177269994947?_skw=itc-1&itmmeta=01KDM1XXVVPQV06298ZWTQ8D2X&hash=item29461d75c3:g:~3oAAeSwtixod-PR&itmprp=enc%3AAQAKAAAA4FkggFvd1GGDu0w3yXCmi1eBjoqJrhIXWn%2FkCXoj%2FeMVXiaBUax6YIHbd6O%2FiKp4PH64%2BO6WmP7kGn1Tk2UMcK1rq7P6DsnFptkFrY1PQowZXrWVndarDf1BPZa7BPg8tVCzELTwhdRhLChGmYZN8WXjEO5atscMX5ZBExo5k0juDtSi36sO%2Bso%2B20flov0%2Fl5iN%2FnTGrPon3ZcXWTBTi8snBOIhuz97RESXo70JyBetZudQpEX4sE4Y1acMrYW7qt8N5aBjdFFWrbYqfL8O4WZ%2F9CMsiNumzJg0z1onwtzM%7Ctkp%3ABk9SR47e94HtZg

Alternate Speaker - Dahlquist DQ-10 ($699)  https://www.ebay.com/itm/357915612315?_skw=dq-10&itmmeta=01KDM1T2XYDNAWJXV6W2YZ92B2&hash=item53556ed49b:g:u0gAAeSwPJRpG4lJ&itmprp=enc%3AAQAKAAAAwFkggFvd1GGDu0w3yXCmi1efJzv04bO0Os%2BaNLBdFzjPTuqM8E3%2BvESssTEYD%2BFBPq7NgMk3%2BSeeVjS6G8ZOS5eD%2FeKwKWs%2BZNsSr5%2FdGfbDDMrokzqxrAo5qb6JmLzbV8N30929f%2BX0eH1mSFbMLCOQhMC0HPb4cdln3cb3srNcslSBrfF5q87gxriVZEW7%2BmGtRhnbnRIJIbVwMNTls5iGAIMkoKb0%2BDEp%2BZCW2MQ7sX0Ku%2BRDuXfPkjpSkPnPeg%3D%3D%7Ctkp%3ABk9SR46v6IHtZg