bad engine whine through speakers

well there is no gain on the amp really, just input levels and those are set to 2V which is the output of my deck. I do have control however through the decks subwoofer adjustment because i have only one set of preouts which the sub amp and speaker amp are daisy chained. so when i turn this down to get no whine, the bass is not at my desired level. honestly i can live with the whine, ive adjusted somethings and its not as bad anymore, and i rarely listen to my music low so its not a huge problem for me. If it starts really ticking me off ill just switch the side of the rca's, and since ive taken my car apart probably 20 times in the 2 weeks itll probably take me 10 mins to do.

I was looking at some eclipse h/u's and i noticed their voltage goes up to 8v. why is this better then say my 2v output? what are the upsides to having that.

Input level *IS* the gain control.  You cannot go by the markings on any amp.  Read the "How to set your gains" sticky post for a proper procedure.  As far as "daisy chaining" amps, most amps with line-level outputs are simply pass-troughs and the input sensitivity (gain) setting on the first amp does not change the level of the signal being passed.  You need to set both amplifier gain levels separately.