I put in the same Polks. I did that, and I have had the dash out 3 times now. If I were to do the speakers again, I'd leave the dash in.Yeah, you can, but if the speakers that you are putting in (Polk db521's in my case) are big enough to require much trimming of the speaker holes it is a whole lot easier and cleaner to do it with the dash out. The 5.25" Alpines that were the stock rears in my car dropped right in, but the frame on the Polks extends out all the way to the mounting edge. Either way, it's easier with the dash already out, which his is.