Just to add to Stupek's answers, you should indeed go with the aux copy. Regarding the second MA though, you don't necessarily need it. It really depends on your needs.
If you can present your DR disks to your local HQ MA, then you could do a "local" aux copy from one library of your HQ MA to the 2nd library (pointing to your DR disks) of your HQ MA.
The drawback is that in case of a disaster, you wouldn't have access to an MA to recover the data at your DR site and would need to set one up manually. If the extra delay is acceptable to your company, then you might be able to go with just one MA. If you can afford it though, I'd recommend adding a 2nd MA over there.
In our case, our DR already have a VMWare environment so I didn't buy brand new hardware for our DR MA and just created a small VM that acts as the MA.