I hear what your saying Shazzam.
I've had ally plates in my 748 for about 18 months now. I changed for the very same reason...to reduce the rattle, which I know some poeple love...but it got right on my bits after a while!!
I did not change the steel basket because when I bought the plates from JHP I was told by the man himself that I could live with not changing it over to an ally one (even though I was willing to buy one from him at the time!). Also the basket can be a bitch to change if you don't have the tools.
I checked the plates over for the first time since installation the other week and yes there is a little 'mushrooming' on the tangs...but very little...certainly not a lot to worry about.
I think the situation would be far worse if you had steel plates engaing with a ally basket...it would look like shazzams picture in no time.
If you can afford it...change both. It would be quiter still, and the reduced wear which will mean it will remain quieter for longer, and last longer overall.
...and yes, it is a damn sight quieter
