I stumbled across this last night while browsing through Amazon.  At first glance I thought it was another laughable bin-filter offering, but in between the lines the description implies that it *is* a dual-cyclone machine, Eureka's first since the 4880AT of the early-2000s.  Good news, no doubt; by this time I was wondering when, if ever, Eureka would bring out a dual-cyclone again.  It appears that this machine has not been out all that long, only for a few months.  
Here is the 6510A linked on the 
Eureka site, and on 
Amazon.