Stoked,
First, there is validity to what your installer has said regarding creating an enclosure for your 6.5" speakers. In a car you have a speaker set up engineered to use the door cavity as an enclosure, so to speak, and the cabin space to give you the bass extension you're normally use to. In a boat you have no cabin to "trap" the longer lower frequencies, and you possibly have too large an area behind the side panels(maybe the length of the boat)for the speaker's driver to work with. Result is a floppy driver producing low to no bass and will probably grenade due to lack of woofer control. A lot of guys with systems have their speakers crossed over at frequencies high enough that this is probably not an issue, because low frequencies are not playing through the speaker.
Depending on what you're looking to get from your stereo system, there are several ways to complete it to your liking.
If you like the output the deck provides and it has a sub preout, you can add a 10" or 12" subwoofer with a 250 watt mono amp to fill the bottom end. You can make boxes for the 6.5's, or cross the lower frequencies out. If you decide to build boxes for the 6.5's, contact the mfg. for enclousre specs.
EDIT: Sorry hit wrong button. I'll finish up.
If you want to play a louder, cleaner, and have more system control, you can run a 5 channel amplifier. 1 channel for each 6x9, 1 channel for each 6.5, and the 5th channel for a 10" or 12" subwoofer.
If you want to have screamin mids and highs and good bass response on a budget, you can run a good 4 channel amp in a 3 channel mode. 6x9's and 6.5's all run off the front 2 channels(2 ohm parallel load ea. channel) while the 3rd and 4th channel are bridged to run a 10" or 12" sub woofer.
Reason I suggested one amp and 1 sub is because you say space and weight are a factor, and good sound is to be had with quality gear and installation.
Hope this helps.
BTW, That is a really good deck.
[ September 05, 2002, 11:09 AM: Message edited by: ROZ ]