Suggestions for bookshelf speakers that have great dynamics, budget of $500 used.


So I really do not know where to start with bookshelf speakers as not been in the market for any for ever it seems.
This is for a second system where a pair of Monitor Audio Silver 3i are currently doing duty.
Room is largish and open but ultimate sq is not the aim as it is occasional use only, but when I do fire this rig up I usually like to play fairly loud.
Sources are many, fm radio, cassette tape, vinyl and streaming.
I have plenty of horses to feed them so even inefficient models can be considered.
Prefer to buy used as big savings to be had obviously and already broken in.
So suggestions around a maximum price break of $500 used.
Thank you in advance.
128x128uberwaltz
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Some great recommendations on this page. My 2 cents is to check out Accessories4Less that has several new bookshelf speakers in your budget including shipping: KEF, Canton, and Focal speakers. You can check them out at the below link. 

https://www.accessories4less.com/
I like my Heresy IIs a lot and would recommend them. I tweaked them a little with some Crites crossovers and tweeters. I think they may surprise you.
I deeply appreciate all the great suggestion that folks have come up with and I am now a lot wiser on monitor speakers!
I am going to look at a local pair of Vienna Haydn tomorrow morning, price is very fair.
Anybody any experience of these?
It’s one brand always been on my radar but never tried out.