Let's assume you already have a darn good system, i.e. speaker choice that sound darn good in your room. Beyond your budget 'might' give 'better' results.
Oh boy, what a deal! You skipped the first question, even free, will they be 'better'? Likely, but not always the case.
"Deal or No Deal?" There is little risk in acquiring a great bargain in good shape, you will be able to sell them for a profit later, soon if they don't work out, or later if a magic new technology is invented (likely very expensive).
I am 70, been involved, auditioning quality audio products for 50 years. My lifetime favorite speakers, current, were designed and manufactured in 1956. Drivers from Fisher President II console, Electrovoice horn tweeters and midranges, and 15" woofers, original crossovers, in a new enclosure designed by me, Electrovoice engineers, and my av consultant way back in 1978.
I have re-coned the woofers twice, the horns proven by 60 years to be bulletproof. I have a full spare set of drivers anyway, to keep them going for life (mine anyway).
Over the years I have acquired some great bargains, including speakers, the category subject to more audible change than anything else without doubt, the heart of your question. New designs with easily perceivable results will assuredly come.
However, stereo tape began in 1956, stereo lp in 1958, the quest for 'better', at any price, has also been going on for over 60 years. Change? People with Quads (i.e. .. ) are like Charlton Heston, good luck prying them from their dying hands!
The best deal in the world on an unknown sound, even if perfect shape is unwise. Search for reviews, find an expert with experience who might have heard them, all while checking out the condition, the first thing to check is the driver surrounds.
