I've run Bilstein B8 on my E90 in the rear for a few summers, will add B8 in the front as well (around 140k km/ 87k miles now) and just adding the rear ones helped quite a lot with comfort (yes). One of the genuine shocks was on it's way out but not too bad before I replaced it. I've got the early m-sport springs on my 1/2006 325i.
And as of my experience with my E46, B8 can be quite harsh in winter on uneven roads. I've also got a set of B8's (with lowering springs) my old Volvo 740 and thats quite harsh actually.
For my little commuter Audi I went with Koni STR.Ts which seems like a fine price/performance offering, did look at the Special Actives too but the STR.Ts where found with good pricing so they made me an offer I couldn't refuse..
