Help in putting together my system with used equipment on Audiogon and eBay.

Whatever you buy, replace all of the caps.  Not really. I just wanted to say that before the tweaknerds did.

You could go in so many directions depending on music tastes.  And you mix one wrong item and it is money wasted.  I like a mix of warm electronics with a bit snappier Speakers or vice versa.  If all
your gear is warm it could start to get muddy, if all sharper it could be fatiguing.  But that is for my ears.

And I wouldn't get into the old discs if you don't own any. You likely are not missing the specifics of the nostalgia so why go into that now, learn the gear with what you know for now. Maybe later out of curiosity. but for now put the money in what you will use.

Now I can't answer what you should do for your ears.  But for mine and my style here are some components I would consider. 

New or newer gear for speakers generally for me but not always.  (I don't mind having a warranty). 
For a warm system that is loud but clear and not deafening.
KEF R11 new, break them in or find a recently used pair. 
Paradigim Prestigie are a bit sharper so I might get a warmer set of electronics like McIntosh or a nice warm tube set for those.
B&W if you like, but then I would go with 802s and the older ones.  Great as a studio monitor but they are not warm.  But I loved the details.
Eggleston if you can find a good pair.  But bring a strong friend they are heavy, and they do like power so you want a strong amp too.
I also like Nola smaller, I hear the larger ones they have made are great so I would audition those, but I hear you will want a warmer amp.

Electronics I like my Arcam amps I like Parasound preamps and got a P3 but have not heard that mix together yet. but for a really warmer sound McIntosh I loved my older ones both amp and pre.  My friend loves them with his Klispch LaScalla (spelling?).  Of course you can get some good deals on Krell equipment and they are a good bet, but not sure which specifically I would go with.  If you want to go old school and warm try the early Superphon preamp.  But you will need to get out of the chair to change the volume this is as basic as you get.   

DAC I don't know enough about the best so I would experiment with any well know brand.  Might even try the Schitt since a surprising number of people have recommended it.

Just some things to try, but the key is try them.  If you like your current Pass Labs then keep it and bring home the speakers you think will compliment it. 

Good luck

I went to Best Buy to visit the "Magnolia Room" and listen to some speakers. All I have to say is WHAT A JOKE that was. There was not one person that gave a damn that I might be there to spend money on speakers. I think they have to stand there with you and switch to different speakers with an electronic switch so nobody wants do that apparently. I probably would not have bought them there anyway. Some Martin Logan's, B&W, Nothing I particularly wanted anyway.

I too am retired military in Jacksonville. Go to house of stereo on the southside. They are a great shop and have a good selection of high end gear. I have been doing business with them for over 20 years. I have demoed equipment from them, they are very accomodating.

Going back to your first idea to buy speakers that are very expensive new and get them for about half price on audiogon, my suggestion is to take a look at the reviews for Sonus Faber Olympica line of speakers. They Olympica 2's cost $10,000 new but there are 2 pairs for sale right now on Agon for $4500-$5000 (or make a lower offer). Sonus Faber is renowned for the fit and finish and superb beauty of their fine wood and leather cabinets - they will likely be the best looking piece of furniture in your house - but also for musicality that matches the look. I owned the slightly larger Olympica 3's ($13K) for 5 years and loved them, and the 2's are similar in all respects except for size and number of woofers. I upgraded to Sonus Faber Cremonese which are unbelievable and like all Sonus Faber perfect for those who love music made with acoustic instruments - jazz and classical for instance. They can also rock but the sheer beauty of their sound for acoustic piano, guitars, cello, standup bass and voices is hard to beat at this price range. Note that Sonus Faber just introduced the new line of Olympica Nova speakers to replace the original Olympics which means you can find some great deals on the original line such as this one for a new pair at $6500
https://upscaleaudio.com/products/sonus-faber-olympica-ii-loudspeaker?variant=31551768461372&utm...

Just a thought. Good luck on your audio adventure.