Good questions by batuchka as usual. Do you need an amp with these speakers? Will they need to be on a desk or towers ok?
For tower speakers here is a list from a great resale company. Some are price each and some as a pair. I haven't heard all these speakers but all are from great speaker builders.
http://www.audioadvisor.com/product...e&sort_by=ASC&view_all=false&sortby=price,ASC
The Martin Logans Motion 10(or 12's) is a great deal along with the Mordaunt's they did have a deal with Martin Logans Motion 12's which are great for 600.. you may want to call them.
If you want something smaller to sit on a desk that is whole other animal.