ETON Compatibility chart:
https://www.eton-gmbh.com/fileadmin/...st_bmw_web.pdf
JL Audio c2-400's:
https://www.jlaudio.com/c2-400x-car-...-systems-99612
If you don't mind spending a couple hundred more I'd do the ETON's in the rear also.
If you read all the posts on upgrading the 2 series you will find the rears are not that important. The Match Up 7 Amp combined with the front's a outstanding system. The Match Up 7 is a PNP solution and others have just swapped out the amp.
https://www.ebay.com/itm/MATCH-UP-7B...cAAOSwlxddIjcb
HTH,
HAZMAT