I'm using a Transparent Audio power conditioner
Plug a Kill-A-Watt to the wall outlet and plug your power conditioner to it, then you can monitoring the total ampere draw of all the equipment that plug into the power conditioner.
Most equipment only provide spec of maximum power consumption, not the normal usage.
If I put too much on the circuit, what's the worst that happens? It just trips the breaker? Or could it damage anything.
Yes, the circuit breaker will trip to prevent overloading the circuit.