The stock replacement is 4x10 the bigger size only fits with adapter is 6x9 the size of the speaker doesnt affect the wattage,
if your bored go to www.crutchfield.com they have a decent selection, then you can go to like circuit city and see what they have . Crutchfield may be a little more expensive then smurfy city,
but they would be more knowledgable and they give you all connectors/instructions included in the price
I just bought alpine 6X9's. They fit good with the adaptor. One thing about that adaptor- it makes a difference which side the metal clip is used on- passenger or driver. the metal clip will be hard to get on, if you use the pass. side clip on the driver side. The drivers side clip won't fit on the pass. side at all. Don't ask me how I know.
I put Infinity Kappa 6x9's in mine, but if I had it to do over again, I would have just bought one good set of components to go in the concert sound location up front.
All you need is good mids/highs up front, and a sub or 2 in the trunk.
I don't think 6X9's are that great of a "bass" provider. I actually lost bass when I went from the stock 4x10's to the my 6x9's.
For my next setup in my Buick. I am going with a good set of components up front, and a 4 channel amp 50-75W x 4 which has low/high pass crossovers on both the front and rear channels.
I'll use the front channel of the amp on high pass to power my components, and the rear channel bridged on low pass to power my 12" sub.
This is a very inexpensive setup that, I have found, works great.