is there anything specific that you're looking for in a sub? maybe the amp integrated into the sub box? fits in a corner? are you willing to loose your entire trunk to the sub?
personally, i wouldn't recommend rf products--imo, they have been pretty poor in terms of overall quality/output in the last few years.
regarding the links that @
tmcmullins posted:
the first one is part of a nice product line, except that it is a 12" sub in a ported box(ported boxes are larger then sealed boxes), so fitment in the car might be difficult-- the trunks aren't all that large on these cars.. but i've heard similar subs as those, and they do decent-- no earth-shattering bass, but fill in the bottom end well. that is a nice package deal though..
the second one, note that it does not include a sub box at all. boss stuff gets a lot of crap in the more professional industry because it's not the most excellent equipment, but i think it would fit your needs well. i don't think that package would be the best though, because the power of that amp isn't needed, not to mention that amp is massive and will take up a lot of space in the trunk. i also don't think that any more then 1-10" is needed at the most.
i haven't installed my sub setup yet in the brz, but from all the reading i've been doing on everyone else's setups, it seems that shooting for installing an 8" sub with about 200-300 watts is perfectly adequate for just about all but the more demanding requirements. just about everyone says it doesn't take much to get really loud in these cars.
as far as what i'd recommend-- i'm going to hold off until you can get a chance to answer some of those questions-- i have ideas that will work for either option, just not sure if you're one of the kind of guys that would like to give up all of your trunk for a sub setup.