Check out the NE GTG results thread, better comparisons from more experienced folks than I there.
At the GTG I heard dual passive caps, Dual DIY LMS's, dual submersives with an F2, a smaller PSA, and brought my FV15HP (with 600 watt amp, but save the hundie for the 550, .5db is nothing to worry about). These are all great subs. I always run my rythmik in max extension mode so when comparing the numbers I'd look at those and not the max output numbers if you were to run it like me.
The caps, submersives, and LMS's were SPL monsters. Clearly another level up SPL wise from my Rythmik. My Rythmik absolutely slams though. Theoretically the servo rythmik should be lower distortion but in the quick, informal, tests we did it wasn't "in your face" sort of audible, I couldn't clearly distinguish in that situation, each of these choices sounded very clean. As far as port noise, I have never been able to cause it in my home and I do dabble around reference. At the GTG we were able to achieve a brief moment of port noise but the tests were absolutely brutal. I really wouldn't be concerned about it and would not let that idea affect my decision.
The caps were flexing the floor above us, small bits of the ceiling were falling on my head, the projector was knocked out of alignment, and they flat hit you in the chest hard. Submersives were similar but their finishes were gorgeous too. The caps were a sledgehammer, the submersive were a shiny sledgehammer. The smaller $750 PSA did a great job, sounded awesome, but clearly wasn't going to dig as deep or loud. It was very impressive and you can't go wrong with them either.
You will not find better customer service than what Brian of Rythmik provides...nor will you find better CS than Mark Seaton, Jeff of JTR, or Tom and Jim of PSA so that's a wash.
Bottom line is we are very fortunate to have these great sub options available. Also check out what Gorilla replaced his dual caps with, the DIY silverbacks are crazy good. Fella with a 3-4k budget. I'd find out what Brian would do 3 FV15HPs for, I believe you will get 10% off each at least. The F25 is near and it is going to be awesome. I'd also be looking hard at the F2, but would really want multiple subs to flatten the FR. Not dinging the cap's or PSA at all, you can't go wrong there, but I'd be leaning toward seaton or Rythmik. My 2nd FV15HP is on the way so clearly I am very pleased and stand behind the direction I went. With my budget if I went more expensive it would be awhile before I got to the duals, and multiple subs are a huge gain over a single due to a flatter frequency response, so the Rythmik was the right choice for my situation. You fellas are definitely looking in the right direction with the options listed. Funk should prolly be in the list as well.