ive been doing some research on these for a while and upon research i hear that most people want 6.5 instead of 6x9 because of the bass and sound quality...then i found these 6.5 shallow subs by kicker and these 6x9 to 6.5 conversion plates...i might keep it simple and do regular 6.5 but this might be a good bass set-up

here it is

kicker 6.5 shallow sub




and the 6x9 to 6.5 conversion plate




so actually i have 2 questions

6.5 or 6x9

and

would this be a good setup

 

and also runa an amp to these

 

You will have zero mid-highs in the rear with these. If that's what you want then sure go ahead.

You do plan on mounting these in place of rear speakers right?

 

yeah

 

I wouldn't be against using shallow subs in addition to other speakers, but if you replace full range speakers with something like this with a very limited range, you're going to end up with a hole in your frequency response. The rear speakers provide a lot of fill and body to the music, and you'll be loosing all of that.

Furthermore, sub's that small are not going to move enough air to get the oomph that I think you're looking for. Theres no substitute for a 10" or 12" sub.