Newbie question: passive volume control mod for DAC

[Ichabod]

Hi, I'm a bit of a newbie to analogue electronics and this will be my first atetmpt at DIY so I really need some advice!

I recently bought some active studio monitors. These are connected to my M-Audio SuperDac 2496 via balanced XLR leads.
The problem is that the monitros do not have a volume control so I can only control it by reducing the digital level at the source... not good!

I am thinking of building a passive balanced volume control. This would require 4xXLR sockets, a good quality 4 channel Pot plus the additional 4 XLR plugs for the leads.

A simpler alternative might be to modify the DAC and add a pot before the balanced output stage. (Would this also avoid input/output impedance problems?) Is this feasible? Where can I find a schematic for the superdac? Does anyone have any advice on how to go about it or what components to use?

Alternatively - is it worth considering an external active pre-amp?

Thanks very much for your help,
Dan