Advice Needed On Vintage Yamaha SpeakersH

Hi all, I have complied a vintage Yamaha system that takes me back to my formative audio years of the 1970’s. It consists of the Integrated CA 810 and matching tuner. A TC 520 Cassette Deck and a YP B4 (B) turntable. I might add a CDC 685 multi disc player to the mix. I’m looking at a pair of NS 20T or NS 500. The NS 500’s have been re foamed and are somewhat local. I can drive to get them. The first pair would be about 50 to ship. Both appear to be in great shape cosmetically as well. I know which are the better speakers but this system is a nostalgic luxury of sorts and will not be actually played all that often. The 500’s are over twice as much. I'm also in the midst of upgrading my main system. I await all responses and thanks in advance. Good sound is important, sparsely played or not.
It seems to me if sound is important, and both are affordable to you, and you know which is the better pair, choice seems easy. 

Then again, the differential in cost could be included into funds for your primary system upgrade. 

Hummmm...    Guess I am not much help here :-).

Sincerely I wish you the best luck in both quests.  
Mesch, no it's a good response. It's now moot. The seller of the 500's just informed me they sold. Bad timing as I'm out of town.  Thanks.
A couple of years ago I put together a vintage Yammy system comprised of a  mint CR1020 and a nice set of NS690 mk 1's.  The NS690's or 670's make for a nice synergy with the mid level Yamaha gear, they're not always readily available but I scored mine on CL, good luck.
Polarin, my original Yamaha speakers were the 690II.  A buddy gave me a pair of NS1000's when he relocated and couldn't take his gear.  At the time I had no need and sold them for a song compared to what I've seen them go for. I'm still hurting over that and will never live it down. I saw some 670's on eBay. I'll look at them again.