I feel that the 308 is a good unit that will outlast it's warranty by a long shot. It's not a very powerful unit, but does a nice job on a 12X12 room. It will produce more ozone than required in such an area once it has been on for awhile. I use one in my truck all the time. It produces way more ozone than my truck requires and I run it at minimum in the truck.
People in the past on this forum have highly recommended the Air-Zone units. I'm afraid I cannot comment because I have no experience with them. I'm not sure if they make a dual unit. Ecoquest is also another viable alternative for a dual unit. The company used to be called Alpine and their air purifiers/ionizers are very good but perhaps a little spendy.
The Enaly 200 and 500 air purifiers are good units that will definitely outlast their warranties, but they are just ozonators, not combo units.
hope this helps,