The Mackie HR824's are excellent. I use them and a pair of Alesis M1 actives. They go for around $1200 a pair. Haven't seen any on the used market but thats probably a good sign. The certificate that endoraver is reffering to ensures that the monitors are a matched set. Basically they ensure thaqt the frequency output of each monitor is the same. I am no authority on sound quality but I can say that I enjoy the sound very much. Great low freq response which means great bass. Also it is one of the few monitors (that I know of anyway) that has some user configurability. It has three settings you can switch to for different types of monitoring environments as well as a high freq cut switch and a 80Hz low cut switch for reducing the bass (like us electronica heads would ever want to do that haha).

All in all a very nice monitor and not too extreme in price.

peace,

fitz