if you run the mids in the back along with 2 12's you will have a focked sound stage - but if you don't care about your sound stage and just want volume - go for it....
Honnestly - I would run a set of seperates - put the mids in the doors in the factory locations and put the tweets in the a-pillars...but then again, I'm more concerned with SQ than pure volume now-a-days...lol
what youa re looking at looks to be decent quality stuff....but Fry's in general scares me with come of the product they carry as far as car audio......so don't limit yourself to just fry's
if you are concerned with staying in that price range, honnestly, to me - they are all about the same....
as far as the power load - what size is your factory alternator?
with suck low wattage requirememnts as are on those speakers that you mentioned I don't see a problem....might upgrade to a yellow or a red top battery when you do the system and go from there!