Thank you for using the Support Forum. Well I am not sure what to tell you! The Phaser 6700 handles paper weights to 80 lb. / 220 g/m2 for duplex. Please take a look at the brochure.
You do not mention which ColorQube you are considering. There is the ColorQube 8580 which will duplex up to 100-200 g/m2 (37-44 lb) but also handles paper 8.5 x 14 / legal. Please take a look at the brochure.
The other ColorQube is the ColorQube 8880 Which has the same paper specifications as listed above for the ColorQube 8580. Please take a look at the brochure. Please consider contacting Xerox sales at 1-866-460-2248 Hours: M-F, 8:30am - 8pm ET for additional information or to ask questions.
Working on a Mac (OS-10 Yosemite) printing approx. 1500 pages per month for an in-house brochure. Each page (8.5 x 11) is a full-page, full-color, high resolution architectural photo (TIFF's at approx. 40 MB's each). Must print both sides and be able to take heavier stocks. Other use is very basic so either is fine. The brochure is critical. Currently using Phaser 6360-DN. Torn between the Phaser 6700-DT and the ColorQube.