Subwoofer decision agony for serious music-only setup... please help

[Pete Basel]

Ok, so if I enter 130W for "System input power" I reach the 8.4 Xmax of the DCS205-4 (give or take).

The bad news is that in order to keep the port velocity under 17m/s I need a port that's 3.75" x 32.20"... sounds like the port isn't making sense.

You have just demonstrated why a PR is often required for small boxes. You get port mass
without taking up box volume.
On the other hand, if you must use a port try 2 to 2.5" which will probably work good enough.
People here are stating that port chuffing is the issue, however there was a JBL paper that
showed 3 dB of dynamic compression going from 1W to 100W with a port that was too small.