Looks like Ray beat me to it, the vendor that Heedz was thinking of is most likely IA Performance.

Subar Stereo Parts -

 

I used the PolkAudio
DB651 6 1/2 for the front
DB521 5 1/4 for the Rear
Got my adapters from
PVC Speaker Adapters - CNC Machined - In Stock or Custom Made They ended up being free because they asked for my installation pictures since they didn't have them for a 07 FXT and I was happy with the way they fit and the quality.

Here's a link to my installation photos
2007 Subaru Forester 2.5 XT rear door speaker installation - USA - View tons of car speaker installation photo galleries

 

+1 on what most other folks have said. Get the spacers and go a little bigger 6.25", ideally get some amount of matting (Raamat as a cheaper and good option).

I sound deadened and ran Poly DB 6501s up front in my '05 in the stock tweeter and driver locations. Needed to back off the tweeter a bit (with the supplied jumper on the crossover) to avoid it sounding shrill, but it worked quite well, with DB521s in the back. There's room for the crossovers behind the door cards.

 

bump! about to order the pioneer AVHX1600DVD head unit and looking to upgrade my front speakers. any suggestions for easy to fit speakers for an 06 sit?

 

All you guys going with the 6.5 or even the 5.25 speakers... with the spacer didn't it push the door card out?

I tried this to mount Polk DB650's but the spacers that Crutchfield supplied didn't work, the door card looked like it was going to be pushed out, and I wasn't sure the magnet would clear the window.