first time poster, long time lurker.

I guess I am a novice in regards to audio and 6.5 in the front of my 08 Hatchback. I have done numerous searches on the site and think all the ideas for this vehicle are awesome.
My issue:
I have tried to research the depth difference in the Polk DXi650 and the Polk DXi650s. I can't find a difference in depth for these speakers even though they both have 2 inches.
My question is, should I be able to put the DXi650 in the front of my aveo with a one inch spacer. Does anyone know the exact depth to avoid? (ie over a certain size)

Thanks so much for the help in advance.