Best speakers under $500? Fire away!

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. 

with the dentons and wharfedale in general, you would not believe the quality of the cabinet, the grill,  and binding posts you get for the money.  
In terms of sonics, they are on the warm side, mellow, laid back, very smooth and zero harshness highs, easy to listen to.  I have them powered by a marantz integrated that is also warm and laid back, and I do not feel like it is a good combination.
They are not monsters of details and air, nor do they fill the room, but that is compared to my totem hawks. They image ok, soundstage ok.
In my room, they are good for low to moderate volume listening, toed-in on axis 8ft away.  If the 3020 sounds like the NAD integrated I once had, dynamic, punch in the lows and the highs, then it could very well be a good match.
The dentons need power, more than my totem hawks.