Welcome to the board.

I don't think there is a big difference in availiblity of aftermarket parts with 6th gen I4's and V6's.

Motor: If you want to go all out, Comptech makes a supercharger for the V6 that isn't availible for the I4.

Exhaust: There are headers, cats, cat-back systems, etc.

Maybe if you are more specific about what parts you are looking at, you'll get some answers.

And about the light housings...the headlights are the same on all 6th gen accords....coupes, sedans, V6, I4, doesn't matter. Suspension components like springs and shocks are the same for coupe and sedan. I think some manufacturs use a heavier front spring to compensate for the added motor weight of the V6.

Comptech is one company (and a reputable one at that) that pretty much only offers stuff for the V6 Accords. Headers, exhaust, etc. http://www.comptechusa.com/

I'm not sure of all the differences in the V6 and I4 parts, but most are the same. I know the exhaust systems for the coupe are shorter than the sedan's.

Hope that helps a little.