These are some very good questions, and this is probably the best place around here to ask them. The information available at Chang Lightspeed would suggest that their line filters are also intended to provide surge protection (at least as far as this mechanical engineer can tell - the EE's in the audience may be able to give better opinions). I'd suggest giving Chang Lightspeed a call.

A good surge protector should be able to protect equipment without overly restricting current, but for power amps you really do have to keep an eye on that. Folks around here have had good luck with TrippLite, Panamax, and Brick Wall for surge protection, if you feel that you need some supplemental protection.