Wait a minute the dac is non optional now on the hr amp...
I guess you should stick to the dac/amp solution by headroom then. I still think you're better off getting an older desktop balanced without the dac, then using the vda2. It's a separate dac with a separate power supply, simple discrete output, yada yada... In my opinion the vhp(single ended, unless you buy two and then fiddle with cables and adapters) is just not in the same league as the hr balanced desktop for very obvious reasons...
I listened to the vda2 sans power supply with my own amp and hd580(single ended), and also listened to the hr balanced desktop with balanced hd580(at a meet) and would be happy with either. To be honest the vda2 is one of the few dacs in the world I would actually buy myself, and also the hr balanced desktop.
So basically, if you can, scout for a used amp only hr balanced desktop, and then get the vda2 and run the dac in balanced mode, otherwise having just the headroom combo isnt too shabby either. I just prefer both