I have been re-evaluating my audio situation, as well. It might be helpful to advise specific models of each speaker and their respective RMS ratings. My recommendations below could be terrible if your 7,7s are rated at 150W RMS. I had a bit of 12V experience in the car world many years ago. In general you should shoot for ~75%+ of the RMS rating of the speaker to be able to drive them with authority and not be underwhelmed with their performance, avoiding clipping, etc
For reference, I have an M600/6 amp and an M200/2 amp and 2 pairs of MX650 (one pair in bow, one pair in stern), MX770 tower speakers and 2-10" M10IB3 subs.
My MX650's are rated 60W RMS. They will sound lousy with less than 20W (your factory head unit likely puts out little more than 10W per channel). The M600/6 is 2 ohm stable, I was able to wire both pairs of 6.5's in parallel using only 2 channels 2X100W@2ohm, effectively 50W per speaker. After proper tuning and gain settings there is not a lot of difference in output or sound quality by taking advantage of the 2 ohm stability. I did potentially lose the ability to balance the front 6.5s vs the rear 6.5s but never messed with the fader for the 6.5s any way. Same 2 amp channels on a single pair of speakers are 2x75W@4 ohm. I think you can see the benefit. 2 ohms load is obviously harder on the amp but if you are using JL Audio, Wet Sounds, maybe mid or higher end Hertz, Fusion or Rockford Fosgate they likely have 2 ohm stable amps.
Spend no money option:
Channels 1&2: You could try running your bow 6.5s and cabin 7.7s in parallel (2 ohm load) and free up 2 channels on your M600. You could set-up the crossover a bit higher 90-100hz and let the subwoofer cross a bit higher, but you then nullify some of the capability of the 7.7s, but you could likely be driving these 4 speakers decently using only 2 channels. Do this first and be honest with yourself if you are getting enough out of the 7.7s- will affect all recommendations below.
Channels 3&4- I'd guess the 8.8s need more than 75W to do them justice, but try it... it won't be terrible. Unfortunately, if this does not get you the result you want, I have found the JL Audio M line amps kinda stink for this application, to drive your 8.8's you almost need an M400/4 ($650) running bridged to get 180Wx2@4 ohms *JUST* to drive your 8.8's. Stepping up to bigger power in MHD product line is double the coin.
Channels 5&6- you are golden, as-is- if your 10" IB is an M3 level JL sub- they will sound great with 200W
Spend a bit initially , but net out only a couple hundred out of pocket:
Buy an M800/8 and sell your M600/6 on the classifieds here.
Now you have 2 extra channels to work with and you can run the M8.8s bridged on channels 4&5 / Channels 5&6 and give them the power they likely need. This is probably best option if the 7.7s do ok running parallel with the 6.5s
Spend a lot option:
I also really want to keep my system all JL Audio but the Wet Sound SYN-DX series just offer a lot more bang for the buck, especially for something like your 8.8s. SYN-DX4 is 4 X150W RMS @ 4 ohms... less than $600 shipped with promo code EDDIE10 (credit to
@jacoviii)
Wet Sounds SYN-DX Series Marine Amplifiers | Babbitts Online
Adding the SYN-DX4 to your M600/6:
M600/6
Channels 1&2- bow 6.5s
Channels 3&4- cabin 7.7s
Channels 5&6- IB 10 sub
SYN-DX4
Channels 1&2- stern 8.8s
Channels 3&4- open for future nonsense (12" M7 sub)
