I replaced all of the speakers in the cockpit. I have 2 pair of JL 8.8 (M880-CCX-SG-WH) and 4 JL free air 10" subs (M10IB5-SG-WH). I have an old JL e6450 and some sort of Coustic amp neither of which I think are a good fit for these speakers.

Here is what I am thinking.
1 - M800/8v2 for the 8.8's
2 - M600/1 for the subs

Not looking to break the bank, just want good efficient quality power.

What do you think?

I think the subs need more power, the 800/8.8 combo should rock.

I had a JL Slash 500/1 running a pair of these subs in my old boat and it was decent. I was thinking that having 4 subs and 2 of the 600/1 amps would be enough.

Get one Wetsounds SD6 and you can run all those speakers off of it and still have room to add more. You could also use an SD4 for a little more power.
SD6 CH1-4 4 subs, CH5-6 4 M880's or CH1-2 4 subs, CH3-4 4 M880s, Ch5-6 extra or Rev410
SD4 Ch1-2 4 subs, CH3-4 4 M880s

If you wanted to go nuts
SD2 1250w @ 4 ohms, run all four subs off it, each pair in parallel to make them 2 ohms and them those in series to create a 4 ohm load for the amp. 312.5w per sub! Probably a bit much.

I am running 4 JL subs on my SD6 CH1-2, CH3-4 4 M880s, CH5-6 Tower pair of M880s ETXv2

Agreed, when I only had 2 JL subs I ran them of an old M1400 and they sounded great. Even though the SD6 is only giving them 145W they way I have them configured they are louder than with the 200W they were getting from the M1400. So I have a feeling the SD6 ratings are conservative.

I will have to look into Wet Sounds, always been impressed with JL. It is hard to compare apples to apples. The JL stuff I listed above gives 200 watts to each 8.8 and 300 watts to each sub. More money than the single SD6, but I don't think it would have the power at only 185 or 290 bridged - but you did say you feel it is under rated. You list 4 subs on only CH1-2 doesn't seem like much power to them, but 4 subs working together may not need the power, I guess the same can be said for the 8.8's....

Thanks for the reply.

If you were closer I'd tell you to come hear for yourself.
The JL specs you are quoting are at 14.4v, at 12.5 it would be 250w to each sub and 180w to each 8.8, but JL has also been known to be conservative with the ratings. Also remember much easier and less expensive to install one amp vs 2 or 3 or 4. Either choice for amps will sound great.

I run 4 10 inch slim line subs off a hd 1200 jl .. they sound incredible .. its all about power .. more power is always better than underpowering in my view .. I also ran 4 10 infinite baffle jl of a m1400 back when ,and thought they sounded quit nice ..

How do you have them wired 1 ohm or 4 ohm? or some other config.

I misread your post as that being item #2 on the list, not quantity 2.

Good plan!