Other than the bulk, a larger diameter power cable is all good. (You are right about the 14Gauge cable sent with the M2500.) Those little electrons want to run freely, as fast as possible, without banging into each other (EE Students ignore this sentence) or without being restricted.
The 15 amp strip will work. When you get to a place where you want to "Release the Kraken" and continuously play at full volume you may need to go to the wall but I doubt it. As I mentioned a bit earlier, the Hypex power supply running the 2500 has a very large capacitive reservoir. It is designed to run three Hypex 2500 watt amps simultaneously and that is where we begin to be concerned about the available house current. This over-engineering helps us a lot in the real world.
Everything we build and test is continuously monitored in the shop for current draw, and under normal conditions a single M2500 draws less than 5 amps. On paper, we can draw as much as 28 amps at full load from that power supply. I have not seen anything close to that with a single M2500.
And before anybody asks, "No," I will not build up a 3x2500 watt version.