1.personally, i prefer individual amps over all-in-one models. mostly because it is easier to match stuff then to build the system based on the available power from the amp(most 5 ch amps seem to have minimal wattage for subs..)
though, in a tight install location, a 5ch amp will save precious room.
other then something else to spend money on, it is useless. caps are good for the first heavy 'bump' of a system(they are used on large motors--like home air conditioners because of the heavy startup power that a/c units require), and after that, they just become a parasitic load on your charging system. in fact, many spl competitors do not run them because they can get higher spl numbers without. though, i am still looking for data to prove that they could increase the sound quality of a system...
they are really not recommended because so many introduce noise into the pc system, and cause even more problems. a dc-dc solution will be much quieter.