amp, speaker wiring

Ok, got the picture. Since I don't have a scope to zero things in I used the 3/4 volume trick and adjust the gain until I reached the loudest volume I was going to use.

Still no one has answered the question on what the best and highest RMS speakers they have use with success.

Any better idea's on setting up the amp?

Don't adjust the gain dependent upon volume of sound.  Adjust it dependent upon onset of clipping.  A simple and very effective way to hear a clipped signal is to listen to a sine wave that has been recorded at reference 0 db.  You can record test tone frequencies from http://www.realmofexcursion.com/main.html

Record freqs in the operating range of the speakers you listen to.  If sub, use 50 Hz.  Mids, use 500 or 1000 Hz.  Don't listen to tweeter freqs by themselves;  you will fall off the boat and drown.  I would suggest using 400 Hz as your test tone as you have only one amplifier to set gains.  For me, 400 Hz is pleasing.

Your goal is to adjust amp gain while playing the sine wave using a head unit whose output is at its fullest but not at clipping level.  3/4 volume on the deck is usually used (but you can use the tones to find this highest level as well, amp's gain all the way down).  When playing a sine wave, the speakers will quickly get hot.  Play the tone in short durations with periods of rest to prevent overheating.  But it shouldn't take long to find the point where the gain shouldn't be further advanced.  The tone will develop a staccato tick sound and change slightly in pitch.  That is the clipped level and gain has to be lowered back to pure sine wave sound again.

On another note, you should get past the notion of paralleling sets of speakers for more power.  Buy the amplifiers that you need to power your system correctly.  You've got a boat, man!