Best speakers under $500? Fire away!

Really hard to beat BA in this category. Their new A series with a return to a dome tweeter is a nice addition. In the used market I prefer the older lines that dont utilize the V metal tweeter. These are plentiful and affordable, although some might need refoaming. 

I would also look into a used pair of Dynaudio DMs. They were significant better than the Elac B6 in every way, when I owned one.  I would imagine that the Elac UB5 is closer to the Dynaudios.  Honestly...you will never be happy with a $500 dollar speakers :p.  I personally would save up and little more and buy either the KEF LS50, Harbeth P3ESR or Vandersteen 1C.    Good luck!  

KEF LS50, Harbeth P3 need save not only a little more, it's 2 to 3 times, it's hard to beat the Wharfedale Denton, the romantic sound, heritage build, and fantastic price

I am testing a pair of Q Acoustics 3020's on the referral from a trusted audiophile who states they punch well above their pricepoint and sound amazing.  
I love the look of the Dentons just unsure how they would meld with my NAD 3020.  

If you can arrange for an in home trial- you can get a better idea of compatibility with your amp, room, music and "ear". A lot of stores will loan out stuff for a week or so, especially if you put it on a card and refund on return. Worst case arrange to pick up their demos on Saturday (with a card charge & return/refund plan), play with them for a day or two (specialty stores are often closed on Monday, or have minimal traffic). If you can, try to get two or three pairs of your favorites at the same time to compare.