I just picked up a couple pair of Rockford Fosgate P163C speakers on a 1/2 price sale.

These are 6.5" speakers.

According to the fitment guide in the store, these will fit both the front and rear doors of my '02 Impreza RS.

Reading around elsewhere, I seem to be getting a different opinion. Anyone know for sure?

5.7 inch mounting diameter (144.8mm)
2.8 inch depth (69.9mm)

Thanks!

 

They will fit in the front with spacers as long as the depth is ok. If you only have the stock factory speakers now, they will be 5-1/4". The upgrade speakers are 6-1/2" and include adapter/spacers that can be re-used for aftermarket 6-1/2's. If you don't have the spacers you will need to buy or make some to get those new speakers installed.
The 6-1/2s will not fit in the rear doors. You can only put 4" or maybe 5-1/4" back there.

 

What about on the rear deck? Could that be where the fitment guide was talking about?

Is there any way to tell what max depth is possible without pulling a panel off?

 

Oh yeah. I'm getting them professionally installed. Not at a big box retailer either, but at a proper car audio place.

I just gave them a call, and their fitment guides say 6" all around.

How hard is it to pull a door panel off and measure?

(not that I don't trust your answer, but it's not the one I want to hear....)

 

The rear deck is not a factory speaker location. Only the doors are.
It's not that difficult to remove one of the door panels once you know how, although the first time it can be a bit tough to get the surround piece off the door handle. There are tutorials on how to do this, check NASIOC and Scoobymods.
If you do have the upgraded speakers in the front you can take them out leaving the spacers and measure the depth available. Also consider the front depth (clearance to the grill in the door panel). If you have only the stock speakers w/o spacers it may be hard to get an accurate measurement because you have to account for whatever spacers will be used in addition to the speakers themselves.
Whoever says 6" all around is wrong. They will not go in the rear doors. The installer would figure this all out once they took it apart, but it would be a bit late by then.
You can try checking with Crutchfield, they have an online guide for what will fit your car.