The D5 USB gets its power direct from the PSU, it doesn't draw power from the Aquaero so no, it doesn't require a poweradjust.
The Aquaero 6 can power a normal D5 directly by itself if that was necessary too, it can just control the speed of the USB version though.
Any D5 pump can work with any D5 pump top so yeah, that top combined with a res will work fine either as separate units
http://shop.aquacomputer.de/product_info…roducts_id=2913
or the Aqualis base unit that integrates them together.
http://shop.aquacomputer.de/product_info…roducts_id=2923
The Aqualis reservoirs are quite large so just make sure you have room for whatever way you want to go.
Edit: Regarding the 37 Watt rating for the D5. It seems most companies that sell relabeled OEM D5's use a general set of specs that include the whole family of D5 pumps including the D5 strong that is designed to work at 24 Volts ... the 37 Watt rating is for the D5 strong model. A D5 Vario does not improve when fed 24V and will only use 2A at 12V in extreme high flow circumstances. In a loop with any sort of resistance the amps used is much lower ... usually less than 1.5A or 20W