Question on amps, if anyone can help?

Are you even in this industry or do you get your information from magazines and friends?  And what is considered an expert anyway?  People that are "professional backyard installers" or people that do this for a living and know the technical side of it?  Don't get me wrong, I'm not saying a new alternator isn't important, because it is.  But not everyone needs to go out and buy one just because their lights dim.  Hell, lights will dim with a 200amp alternator, too.  And at idle, a "high output" alternator typically puts out less current than a stock alternator.  Alternators don't produce their rated output till about 2000 engine RPM (which is about 16,000 alternator RPM) ideally.  No vehicle is ever going to be able to supply all the current that some of these radical systems need to work perfectly, but in a vehicle environment, there is no "perfect".  We can only try to maximize what we have to work with and what an end customer is willing to spend on getting these upgrades.  If a salesman/installer knows Ohms Law and can apply it to make sense to the customer, then they can relay to them that they don't need that much power to get what they want in their system and won't kill his/her vehicle.  Plus you get into an amps' efficiency factor in that no amp will ever produce rated power in a vehicle, anyway.  Maybe one day when we step up to 42 volt electrical systems, we will definitely see some differences.

And, a cap is NOT like a battery.  There are TONS of differences in how they work and what they are there for.  Each serves its' own purpose in the system.  Resistance in a cap is far lower than a battery which gives it its ability to discharge/recharge faster than a battery.

I'm not here to argue with anyone, but the purpose of caps (in final) is to just maximize what we have to work with in our vehicles.  Each does what they feel is best.  But the SINGLE MOST IMPORTANT THING IN THE CHARGING SYSTEM IS TO HAVE PROPER SIZE CABLES AND CONNECTIONS!  Without this, all else is a waste.  The weakest link is what kills.

One of the great things about this forum is that you can get opinions from all sorts of people and everyone is free to express their opinions.  Opinions are by their very nature never "right" or "wrong."  Every little bit of knowledge helps though, and I know I learn new stuff on here every single day.

The alternator upgrade can be done after the stereo system is installed, and it will still take the same amount of time and money to do it then than it would if you did it at the same time as the rest of the stereo system.  With that in mind, i'll have to agree with tdsteele that you should at least get all the stereo stuff installed and play it and see how the charging system holds up.

First thing I would do if I were you (after all your gear is installed) would be to do that headlight test I decribed earlier because that will tell you right away what direction you need to be pointed in.

If that doesn't prove conclusive, drive the truck around for an hour or two at night, under different road conditions (highway, city, parked, etc.) and play around with the stereo.  Listen to different types of music.  If you only have the lights dim a couple of times during your entire drive, and you had been pushing your setup pretty hard the entire time, then I think a capacitor would suffice for your situation.  Clearly all you'd be needing is a little buffer of extra power to be used occasionally.

Just out of curiosity, what kind of music do you listen to?   Cuz if you listen to rap and plan to have your system slamming all the time and playing long bass notes at max power then I can tell you right now a cap will probably not be enough.  If you listen to something with a lot less bass then it might work okay, but the only way to know for sure is to try it all out first.

I never said the cap was an instant fix...just something to do BEFORE wasting money on an alternator you may not need.  And even then, the alternator may not help tremendously depending on the driving habits.  If you are at cruising speeds ( I mean cruising on a Friday night) then a lot of H.O. alternators produce the same or LESS than a stock unit.  It has to be at higher speeds to make more difference.  Everything done in a mobile system is for the benefit of the equipment.  It all works as a team.   But all this should be done after making sure ALL the other wiring tricks are done first.  Maximize the what's there before spending the big bucks.  Bottom line, there's only so much blood you can sueeze from the proverbial turnip.