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
No brainer.  You talk about plenty of horses to drive.  Does this include a sub out on a preamp?  Just add a sub for more throw and keep the Monitor Audio speakers.  More dynamics and bigger sound overall.

Really, FM, cassette, how audiophile do you need to get?
Uberwaltz, yes, I was thinking that $500 would be more likely to purchase a speaker sounding different as apposed to better. I guess it comes down to how much you enjoy the Monitors.  I have 3 sets of speakers for use in my secondary system, change can be fun. Also serves as an educational experience.
Unfortunately no sub out from my vintage Sanyo receiver so if went the sub route would have to be on the speaker high levels, which could work of course....

Mesch.
Now we are on the same wavelength here, and a sideways move could end up being a backwards move, been there and done that many times!
But a change is also always fun and always educational!