Passive bookshelf speakers for $500?
Infinity Modulus, the originals with EMIT-K tweeters. You will find none better. Used they're available for $300-$400 all the time (new retail was $1000/pair, plus $300/pair for stands).
They will make the Swans, and pretty much any other bookshelf speaker in existence, sound paleolithic in comparison. Infinity's goal when creating them was to make a bookshelf system with as much of the performance as their vaunted IRS speakers as possible - and they did an admirable job.
They were intended primarily to go with a matched $2000 servo sub, but those are quite rare these days. If you don't have a sub already, you may want to look for Infinity "SSW" servo subs from the 1990s; they are also relatively rare, but cheaper and will go well with the Modulus.
