Longo, I've done several upgrades up till now on my 09 FLHX. Rinehart slip ons with V&H head pipes, Heavy Breather AC, SERT. To be totally honest I was not totally satisfied with the amout of $$$ that I put into all of these upgrades and little improvemnet in performance. I wll be riding this bike 2 up alot so I was looking for more power as you are. I just installed the SE 203 cams with adjustable pushrods and I now have a big boost in torque. This was money well spent. I'm thinking that the cams pulled all of the other upgrades together.
Just my $.02 good luck.