Hi Tom you would still need a mixing desk. The headphone output on the desk would be connected to the mini headphone mixer and then you have multi headphone options....with a volume control for each set of phones. I use such a system for my home studio. The cost of buying both a mixer and a headphone mixer would be much less than buying the jam gizmo. There would probably be more routing options and better fx plus a graphic EQ superior on this system than what the jam gizmo offers. IMO these gizmos are good for home use but lack the sophistication and routing options of a pro mixer......like this one
http://www.google.co.uk/products/catalog?hl=en&cp=15&gs_id=e&xhr=t&q=mackie+mixing+desk&qscrl=1&nord=1&rlz=1T4GGHP_en-GBGB441GB441&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&ion=1&biw=1366&bih=641&wrapid=tljp1342259100247024&um=1&ie=UTF-8&tbm=shop&cid=14852464228977072788&sa=X&ei=nz8BUNncNaaa1AXH8oSBBw&sqi=2&ved=0CGwQ8wIwAg
This Mackie mixing desk prices at around $300..... add about $50 for a decent headphone mixer and it comes to less than half the cost of the jam gizmo. I would also bet that this would have a better spec and quality of components. Even this option would be cheaper and has far more input/output options....plus usb capabilities.
http://www.google.co.uk/products/ca...OEEBUORNgr_RBdm0wMIH&ved=0CHoQ8wIwAw