You need to mount the cap as close as possible to the amp (less than 12 inches). It needs to be wired with the same gauge wire as well. I would get a full farad instead of .5 in case you upgrade in the future and they aren't much more money. I don't have any subs yet, so I am not sure if the lights will dim or not, but I am going to add a cap even if they don't because I personally have seen/heard good results from them in the past.

I am willing to bet that at idle your lights will dim, from the other posts I have seen about lights dimming. If you have an UR pulley the need for increased elecrical current is increased as well.

Aaron

Just to let you know, I run a 600a5 Rockford Fosgate amp (50Wx4 and 100Wx1) with no problem of dimming lights. It is a meaty amp and so far no problems........so go for no capacitor first and if you have problems add it in later

Anything less than 1 farad is pretty much worthless as you won't notice a difference.
I will tell you this I noticed a difference wiht my soundstream(has more builting capacitance than any other amps) when I was running a 1 farad cap mainly in the tightness of the midbass and sub bass(since they draw the most current). Another option is getting an optima battery(better deal) I got rid of my 1 farad cap and have just that and notice only slight light dimming at full volume with my conntinnium(soundstream 660w rms 5 ch amp).
Rich

for a 500w amp am I going to need a Capacitor to keep my lights from dimming? Also whats the best mounting location for an it?

Originally posted by MPREZYA:
Another option is getting an optima battery(better deal)

I've been thinking about getting an Optima. Do you know of any good deals on them?

I have an optima battery in my car. I still have a major headlight fade problem. The battery did not help me out very much. I don't know if is cause I'm running a lot of power or what.

I got mine for @$135 (red top which isn't deep cycle) from a local shop (interstate batteries offers them just rebadged). I would say if you run over 1000 watts get the deep cycle and or a cap. I have never had a problem with the Optima red top I even was able to drive my car for almost an entire weekend with a dead alternator that should tell you something.
Rich