Size of the rear speakers in a MK5 Golf TDI 1.9 with standard RCD300 audio

[Trumper]

Hi all,

Not sure of the size of the rear speakers in the car. I know the front can do 5 1/4 to 6 inch but the back no idea. Does my golf have splits in the front im assuming so.

Looking to put an amp and new speakers behind my RCD510 so i am in planning stage.

So far for the front looking at JL Audio VR600 CWI splits
For the rear just putting in JL Audio C600X C2 (I have these already)

Amp would be an Alpine PDX-5 5 channel

Possible sub would be Tw5v2

Any thoughts in fitment or if i have no idea what im doing chime in.

Any constructive advice im happy to get. I think with would sound great but im no guru. I have no idea what pushing a soundstage is explains my car audio skills.

Trumper