Is the Asgard 2 + Modi a good combo? or should I just get a Vali, is it even worth getting the Asgard?
The Q701 may or may not be switched out for a Fidelio X1, or DT880/990.
I've found the O2 and Asgard 2 to be very good all-arounders for their prices, which are about $100 apart. An all-arounder is probably what you need, given the diverse set of cans to plan to throw at hyour amp.
Can't help you with the DAC issue, as I almost never use a stand alone DAC.