I want to set up a 4.1 surround sound "square" (5m x 5m) at the end of a long room (5m x 18m) for an art installation which will run for a few months, where participants will stand in the middle of the 4 speakers (sub is in a niche on the side). I am considering several inexpensive active/powered (PA) speakers e.g. Behringer Eurolive B108D, Behringer Eurolive B112D or Samson Auro D208 together with subwoofer DAP Audio DRX-12BA which seem to fit the requirements for the space. I am considering using a 5.1 DAC connected to a PC with an external USB soundcard to connect the speakers via 5 RCA outputs (using a 1/4" adapter). I have found several 5.1 DACs for 25-50 Euro on Amazon, but I am not sure if any of these are sufficient.
Which specs do I need to consider when shopping for an external USB DAC?
Is it required to add an amp/receiver/mixer somewhere in the mix?