What to upgrade to?

Do you listen to mono lps?

I changed from SS to tube preamp and tube amp: thought I was 'done', then joined the forum, ... learned about the real difference playing mono lps with a mono cartridge has over playing mono with stereo cartridge (true), and, I wanted to try a longer arm. Not easy.

Ended up going for a large plinth two arm setup, 9" arm with mono cartridge ready to go, and a 12.5" arm with stereo cartridge ready to go. 9" arm has removable headshell, to use alternate stereo cartridges.

you need an easy way to pick which arm/cartridge. I didn't think about that, fortunately my old McIntosh mx110z tube preamp has phono 1 and phono 2, couldn't be easier, just got lucky.

I got newer tools for lp setup, accessories, and, I found a cleaning/drying system that makes a huge difference for my old lps playing quietly.

Now I think I am done. The lubricant in my reel to reel player and cd player is drying out, I know need to play them just to keep them limber.

I have about 10k in a complete turntable and my speakers retailed for 12k about 5 years. Both I could live with in retirement and be quite happy.

Congratulations! You have done it. Built a system you really enjoy. You should be proud of yourself. Way to go!

But I have $15k - $20k to spend if I want to on either upgrading my turntable or speakers. What would you upgrade? Turntable or speakers?

Wait- what??!?! I thought you just said.... and I said,... never mind.

This is where I get to put in my plug for how people are so totally missing the boat leaving so much performance on the table, sound they never in their lives imagined was right there in front of them just waiting to be unleashed and revealed. But no, instead of that they run out and spend money replacing perfectly good stuff they already had missing a golden opportunity to go so far beyond they could never even believe until they do it. And maybe not even then.

Save your money, bob. Tweaks are the answer. If you spent half of what you're talking about on stuff I know about you would have ten times the sound you could get with any combination of speakers and turntable you're considering now. Ten times. And I'm being conservative.

If the OP is all-analog or at least mainly analog then two complete turntables would be a lot of fun. Get a sense of what the Lenco does versus another topology and all that side by side. Plus if there is a higher mass arm in the mix as well as the SME V the door is open to try all manner of carts!

I have gotten some great recommendations and one mentioned above is a second arm on my table. It is slotted for a 12" arm so that is a possibility.  It has also been mentioned by a few that are familiar with my Intuitive Design Gammas that they are excellent speakers and changing speakers might not necessarily be a upgrade.  I agree they do sound really good.
I don't necessarily want to spend the money just because it's there.  I can always add a better power cord or tube roll.  Sure there are other tweaks that can be made to my system. I guess possibly going to a few dealers or shows and listening to some speakers is a option.  
Again thanks to everyone who has replied.  Any other suggestions I am full ears.