I agree with 2G to a point. Plan your system definetly but buy your amp and sub now. The LanzarVibe1200D is a great amp for the money..Ive been using mine for about 8months four of which have been at 1 ohm.
heres a link to a review on the amp:
http://www.carsound.com/reviews/amps/vibe1200d.html you used to be able to get them from
www.national-electronics.com for $220 but I cant seem to get to the site...anyone know if they went under?
For the sub its best to look at your available power..the Vibe puts out 750watts @ 2ohm...thats a lot of power. Look at some subs that are 2 ohm..example a DVC 4ohm sub can be run an amp at 2ohm, there are a lot of subs out there. Even though the Shiva is not DVC 4 ohm you will still give it a respectable amount of power and for $115 you cant beat that sub... a friend is hitting 150.1 Db w/ a single Shiva setup.
just thought of:
is $450 your budget for everything? you would have to sacrifice a little on the power/subs and get a small amp for your front speaks if thats the case.
sorry for the long and unorganized,
In