Fair amount of work to get those quads to fit right in the pano,
At the very least it'll need wagon quarter panels and maybe even a wags bonnet, then you'll have to cut the panel below the light (beaver panel?)... or alternatively you'll need to fill in the huge gaps the pano quarter ligts leave... It would look good but IMO I like the standard lights look, or go all out and get the DX square lights like stahlz_ae86 (on ke70.com) has.
Re the Cd player just don't throw away the brackets that are holding the original in there, they are the key..
I'm not really the person to ask about webbers, but my engine has had no work done to it so i just put a 32/36 on mine, guess you gotta match you webber size to you plans for the engine/etc.
As for speakers that spot behind the seats is killer, there is also room in the kicker panels if you don't want to cut the doors, I have some 5" in the kickers, they fit okay with a bit of mucking around..
:P