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

Buying used is wise .... I bought for peanuts Mission Cyrus 781 speakers (under 100 bucks) To upgrade that would be buying thousand dollars used speakers (Harbeth probably)... With luck and if you look for you will be the next owner...I cannot say anything bad about them....But they are at the limit of size for budget speakers...They are on my desk between the computer screen on my homemade anti-vibration sandwiches plates...My best to you...

I've seen some good press on the Klipsch RPM600 and I think they're within your budget. 

With all due respect to the previous poster, the Klipsch have nice and lively sound but a bit bright for my classical music ambitions.

Buying used, you can get a cut above that and end up with even more quality, although for the money, the Klipsch is a nice offering, especially for certain kind of music...

I prefer the MA silver over Klipsch.

With your budget, it would be difficult to out do the MA silver - I love mine with pretty top end sound, and clear mid and tight bass...although lacks refinement of an upper end speakers.

I second the Harbeth previous poster mentioned - they would surely lift you out of a side ways move, and give you an upgrade...but would be hard to find for that money...

Perhaps you can look at Spendor speakers as well...