I'll only venture to recommend one brand/supplier:
Everything I've heard about these CDHs has been good.
They are twice as much as the ebay offerings. However, Lavaner seems to do some QA/QC and uses quality parts in their kit. Everything else is a crapshoot in CDH land.
Best practice with the CDH is to run it full power as much as you can. Running them half or low power tends to allow sooting in the unit. Running them full power for 10 minutes after camping helps but even so, over time idling them at lower power allows soot build up. Long term, the higher the combustion chamber temps (full power) the better off your CDH is.
I have a 2kw in my EB with penthouse. In SoCal a 2kw is plenty.
One time camping in Bridgeport CA (6500ft) it got down to 15*f outside. My 2kw CDH was working full blast all night with the top popped. The thermometer never got lower than 55*in the van.
All that said, if I lived in Colorado I'd get a 5kw unit.
Most CDHs with digital controllers are programable for a specific elevation (the Afterburner is too). You just have to go on the Facebook CDH groups to learn the settings to adjust. Not hard to do but takes some time reading up on it.