Not sure what you mean by a "decent" turntable, but if I were in your shoes:
I'd look to get my source up to the level of my amp and speakers. Assuming your table is good enough, a decent used phono pre will set you back less than $200 (even less).
Then maybe a decent new (or almost new) cartridge assuming the one you have may be old and neglected.
Then I'd make sure my room was treated at least somewhat. Don't overlook the room.
Then I'd start to look at less critical things like tubes, cables, upgrading the amp and such.
I'd look to get my source up to the level of my amp and speakers. Assuming your table is good enough, a decent used phono pre will set you back less than $200 (even less).
Then maybe a decent new (or almost new) cartridge assuming the one you have may be old and neglected.
Then I'd make sure my room was treated at least somewhat. Don't overlook the room.
Then I'd start to look at less critical things like tubes, cables, upgrading the amp and such.