SEEKING ADVICE: Which component would you upgrade first?

everyone,

long term advice is great, however OP's budget is being ignored.

"for my budget (+/- a few hundo)."

@lukasread you seem to enjoy your vintage system, so (esp. given your budget) i'd stick with vintagey gear. I don't think i've heard the sx-680, but i owned the sx-780 and it was a really good sounding piece. also consider a kyocera receiver, which are excellent and inexplicably cheap in the secondary market i've also owned the hpm100s, which were fun but inessential--i'd look at trading them for something like polk monitor 10b or ads--the hpm100s seem to selling for a grand on ebay, so you can finance some new toys.

@elliottbnewcombjr half the comments as usual have nothing to do with the OP's question

A few options from someone who has been down your road recently. Not sure I would say any of these is the "right" way to go, but any of them will make an audible difference.

One, I don't have any experience with your receiver, but if you're thinking about upgrading your amp the NAD C316BEE is a great option. It brings that classic NAD class AB sound, and has a really good MM phono stage.

Two, I'll echo the previous post about upgrading your phono cart. A big improvement can be had by upgrading/updating to one of the Sumiko oyster carts, the Nagaoka MP series, or the AT VM that was previously named.

And third, if vinyl is your primary media, think about a record cleaner. I use the Record Doctor, which made a big difference in audible quality of my vinyl for not a huge investment. And if you play a lot of used vinyl, an inexpensive ultrasonic cleaner makes a remarkable difference. 

Good luck and enjoy the music!

Corelli +1, If you know an audiophile near your place try to listen to his system , to see if you like it. Then if you like it. Hopefully he can mentor you to put a low cost system if you don’t have the budget.