What will the difference be between the Panasonic 6800uF in the kit and premium high-capacitance options, like the 18,000 or 22,000uF/50V Panasonic TS-UP ?
Actually, I don't really know. The 6800uF was good enough for fairly deep bass (~40 Hz and lower) on Capt. Rajesh's Kenwoods. Maybe for bass-heavy music at high SPL, like hard rock, hip-hop, disco, etc., there may be an advantage with the larger caps. It may also help to drive large-diameter woofer loads (say 12" or higher) at high SPL.
I just left it as an option for those who would like to experiment - it may well be the case that the overall sonics may be worse with a high-capacitance PSU filter, as compared to something in between, like 6800 or 10,000 uF.