Behr, $140...0E based on what I know. My original went 190K...properly maintained, why think of spending 5 times that on something known to go the distance? Whenever folks try to do better...8/10 times, they don't (I'm making up stats. to support my hypothesis!).
You'll want that money for other things on car...and go 0E whenever you can on critical components and you'll never complain. Search every control arm/bushing/water pump/therm/fluid thread...every one...someone loves, someone hates...My lowly 99.44% stock car is amazing...don't know what cars others are driving that they're not happy with stock handling (other than dedicated racers), but I suspect in many cases, it's getting older bmws not well maintained at all...and thus sucked at handling...so the mods probably improved the situation over it was....anyway...off topic here.
Not seeing any reason for an all aluminum radiator...for the little extra it might've taken bmw to make them that way, I suspect they would have if there was any reason for it...190K miles on mine makes me think you can't improve much on engineering like that.
As desperate as this sounds, in comedy, 'likes' and 'views,' 'friends,' and 'retweets' really help. If I've ever helped you, please help me by friending, liking, viewing, and retweeting. It makes others think I have a following...it'll take you a minute or less. If you could, I'd really appreciate it!
A recent set--NSFW audio: https://youtu.be/_dcxcZfD6dg
Mangofy your E46!