Understood but, done properly, audit tables are never a performance problem nor a maintenance problem. Putting the audit tables on a separate server brings all sorts of problems to the table including (but not limited to) the cost of additional licensing, maintenance of another server (backups, disk size monitoring, security, etc), and does nothing to alleviate the problems associated with index and stats maintenance never mind the complexities of sending data to and reading from that other server.
--Jeff Moden
Change is inevitable... Change for the better is not.