WS-420 & amp advice needed.

I don't speak stereo, but I have a mobile installer coming to my house to install equipment I'll have on hand. I currently have
2 wet sounds pro 80's powered by their own dedicated amp.
My head unit is a Clarion M502
I have 6 in boat speakers 6.5 Polks I believe. no amp currently
I want to add a sub.
I have a WS-420 equalizer still in the box

I'd like to buy an amp just for the 6 in boat speakers. How many channels and watts?

I want a little bass. So I was planning on buying a preloaded speaker box with one 10 or 12
I don't really want to put the sub under the the wheel. I have tons of room in the storage under the glove box area (05 Supra 21V). Can the sub be open air or should it be in an enclosed and ported sub box?

Any help would be appreciated.