No problem Fuji,
You don't need to spend a lot of money to get good sound. There is a debate which upgrade should be done first, the Head Unit or the speakers. The differences will be very evident with either choice. Since you will probably want as much sound as possible, try to fit some 6x9s. There was a post not long ago about the installation of 6x9s. If I recall, almost no modifications are necessary in the front and some very minor work needed in the rear. When looking for the 6x9s, try to find out specs on the effeciency, which will be written as 90 dB 1w/1m or 90 dB 2.83v/1m. The higher the effeciency, the louder the speaker will be able to play with a given input power.
I would also seriously consider a new HU if at all possible. It'll be worth your while to save up for a little longer. There are a number of good values in the 200-250 dollar range including Blaupunkt, Pioneer, Sony, JVC, etc..
Regarding the doors, they are held on by a combination of securing methods, including screws, plastic clips. They aren't too difficult to remove.
I'll do a little searching on the net to see what I can find for you on some 6x8's or 6x9s.
Good Luck.
Dave
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99 SVT
Sony ES CDX-C910
Sony Digital EQ/X-over
Sony Changer
McIntosh MC440M
Adire Audio Shiva
MB Quart/Vifa seperates
