Infinity R162 speakers at ~$200, but you have to wait for them to go on sale or you'll have to pay $450.
These are the best sounding speakers I have found for less than $500. Don't let the fact that they can be had for $200 deceive you. Infinity made a very nice set of speakers with these.
There are two speakers I can think of that might challenge them and would like to hear before being to quick to declare them as best under $500 speakers:
1) The newest version of the AA's with the improved Vifa tweeter. They are no longer available, but the previous version with the Dayton tweeter beat more than a few <=$500 speakers I have heard. IMHO, the Infinitys are a step up from the AA's that I have (Dayton tweeter),but I preferred these (Dayton tweeter) AA's to the Elac Debut B6, Ascend 340, and the Elac UniFi
2) The JBL 530 which go on sale for $300 from time to time (Seems like regular price is either $500 or $600). It seems like I remember they are expecting more in October of this year. Based on my experience with the JBL 580, I would expect the 530 to be more dynamic than the R162 and the R162 might offer a tiny bit more resolution. I suspect (take this with a grain of salt) the R162 may be a better choice if you are trying to get as close as you can to your BMR's with an under $500 speaker and the Studio 530 may be a better choice if you are looking for a speaker to compliment your BMR's with a substantially different sound (without sounding bad).
From my perspective, these two offerings from Harman (Infinity and JBL) which both fall under the same type of intermittent discount/sale strategy represent the best buys currently available! The fact that they are $200 or $300 below your $500 target just makes them that much better.
I have also compared the Infinity directly to the Canton Chrono 502.2 (which has a MSRP of $950, but sells for $350 on Accessories4Less) and the Infinity is a better speaker!
Edit: Sorry Ken, I was typing when you posted. I do consider the Chrono a great deal, and a best speaker for the $350 price, but when the Infinty or JBL are on sale, that changes the rankings, IMHO!