Thinking of changing my suspension setup...

I have a 2006 m5 on h&r springs and 12mm spacers but with stock shocks. Also have Dinan bump stops, Dinan front roll control system and Dinan rear sway bar. Ride is a bit harsh, and I do suffer from rubbing of the rear tires, especially through dips on the freeway. My front tires, however, do not experience rubbing. I always had the inclination that the rubbing was due to the car being too low.
I think my current shocks need to be replaced, but I’m not too sure... (I have 75k miles).

I have the impression that the stock shocks just cannot deal with the stress from the h&r springs. So I’m considering the bilstein edc replacement, but read that these are just OEM replacements and dampening is very similar. I also read that those with bilstein OEM replacement with the h&r springs are very happy with the setup. I’m concerned if I go this route, I may run into the same issue as I am having now. My technician says I should go coil overs to avoid the rubbing issue, especially since I want to go 20s eventually. In which case, I would go with the bilstein edc coilovers. I want to avoid coilovers but if I want the lowered stance and relieve my rubbing issue, I think coilovers is the way to go.

Any thoughts for non-coilover route? Or should I just go coilovers?

Thanks in advance