I am replacing the stick paper cone speakers in my R53 (non-HK).

I read that people are using 5 1/4 and 6 1-2 inch speakers. When I measure my speaker its 5 1/4 with the mount holes are 6 1/2.

What do I order? Look at Kenwoods but not suck on them as long as they are 4 ohm.

 

Decided to go to Crutchfield. They had the speakers, mounts and wiring adapters all in a kit and very good prices.

 

I replaced my door speakers on 02 R53 with 6.5 components, minimal modification to work.

 

I put in Focal 6.5

 

I did 5-1/4.

Remember, bigger is not necessarily better unless one has the power to push them. With the stock HU, power is tiny. Better to choose speakers based on sensitivity than size- a properly matched smaller speaker will sound better than an underpowered bigger form factor.

If one's changing to a higher power (not "Higher Power"!) HU then there are fewer limitations.

 

I bit the bullet and did a full swapout:
Alpine HU
Focal Components in front doors
Focal 6x9 coax in back
400wt amp for the Focal
12" JL subwoofer box with a 500wt amp