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
Been doing some reading this morning.
It may take more than $500 to significantly better my existing Silver 3i speakers.
Did not realize this model was still made in England before they switched production to China.

Tbh, there is not much wrong with them but at the very low price I paid I assumed they were a cheaper speaker that it seems they truly are.
Guess I should just trust my ears, the grass is not always greener on the other side!

Still looking at options though.
Are these actually going on a bookshelf? How big can they be?

Vanatoo Transparent One Encore active speakers are the first thing that come to mind. These do it all well and very compact.  You can buy them new on Amazon for $600.   I use a pair in my wife’s sunroom. 
Actually they will sit on 26 inch high solid sand filled stands so can be a decent size in reality.
I guess monitors is a better description that bookshelf speakers.
But active will not work as being driven by a vintage Sanyo receiver, no outputs bar speaker connections.