The AV folks who will be using and managing the equipment are the best source for determining the evaluation criteria. They can determine the performance requirements for the AV equipment based on the expected uses. If they can identify a minimum set of specifications, the lowest price technically acceptable (LPTA) source selection method could be considered since it can greatly simplify the evaluation process (see FAR 15.101-2). That said, you can search the Contract Opportunities module at SAM.gov using a term such as "audiovisual equipment" to get a better idea of what other agencies are considering. Postings that include attached solicitations will contain specifications/statement of work which can be used to firm up the requirements and evaluation criteria for your acquisition.