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
Vintage:  KEF Q1 (AMAZING SPEAKERS: plenty of detail with amazing midrange and sufficient bass for me); doesn't do well with music like the "AMERICAN IDIOT " CD or Big Orchestral pieces, but Opera, solo voices and Eagles-Kansas-RHCP surprising enjoyable...

Vintage Big Boxes: JBL L25 PRIMA ( funky looking boxes with plenty of jump and presence)

And if I was looking at new: I'd investigate specials from KEF (who sells direct)

HAPPY THANKSGIVING TO ALL!!!
Injust bought a pair of Polk Audio Lsim 703 for 449$ shipped from Audorama. I know most audiophiles do not include them on their list but I personally think the Lsim series is underrated. Retail price on these bad boys is $1,500 so this is a killer deal. Heard great things about them and cant wait to listen to them. Will be using Arcam SA20 and Rega Planar 2 TT. God bless
Edwinf, please get back to us once you have listened to the Polk's for a while.
I second that on the Polks.
I so very nearly pulled the trigger on a pair on ebay at $534
So $449 shipped is a true killer deal indeed!
Please do report back upon listening although as new you will need break them in but would still love to hear first impressions.

Happy Thanksgiving to all!