Glad to be of some help. Yes installing a tweeter in your current setup is a good idea. BUT how are you gonna power it? if you power it with a Head unit the total impedance (load) will increase, may damage your Head Unit.
Get a 4 ohm components or 4 ohm 6.5 coaxial. Power them with your HU and enjoy the Music. This way no big alteration is required.
@faroooch:
Sir that grill can easily be pulled apart with the help of a slaver or a tester. no need to pull the dash apart.
as far as the tweet firing is concerned. Well i did not like my tweets in the dash grills. Reason being the distance from the mid/woofer increased so much, that rather their sound blending with each other it seemed that two different speakers were installed. Sound of tweet and mids should blend seamlessly, thats the aim. In this situation not only the tweeters were off axis, their plane was different also i-e mid firing in x-axis (horizontally) and the tweet in y-axis (vertically)
Tweeter location depends on many many variables. such as xover slopes by the cross over, x over ferquency, power distribution by the xover, etc
You have to use the hit n trial method, use double tape for that, try A-Pillars and kick panels too. You will have to find a sweet spot your self
Hope this helps
Regards.