Hi.. I drive a '98 Lexus LS400 with 7 speaker audio. Splits in the front, One each rear door and sub in rear parcel shelf.  I have just purchased a pair of JBL P550C Power Series 5" splits for the front and for an amp, ive been advised to look at a JBL GT5-A604  4 channel.

Any thoughts on my choice of  front splits and amp I'm thinking of purchasing ?  The Lex also has an 8" dedicated sub in the middle of the rear parcel shelf.  Any surgestions on this ? Like should i leave it alone or what sort of 'upgrade would you surgest ?   Also, the sub is just a free standing (or hanging) speaker with no encloser. I have seen sub's in 'slim' enclosers..... any thoughts on these ?      The stock system is pretty dam good but i know it could be better. I don't know how to describe what i'm looking for... I'm not really looking for more volume as such, perhaps a 'bigger' sound. I want it to sound like i'm in the Opera House.....

     Any thoughts would be greatly appreciated. .. ... ....  Paul R   :)