[pbarb]

Yes I would listen to Joker and invest in some high quality cables. They make all the difference in the world. That is not normal and should not be happening to you. I've had shitty installs (from myself and friends) and top notch installs (from my audio shop) and if its done right your subs shouldn't affect anything (rpms, lights, etc.) even on a stock battery w/o a capacitor. Check every connection, clean your battery connection, make sure every ground is solid and clean, and use good cables, specially your battery cable. Get something thick an able to carry all that load.