The cup kit I mentioned is a very smooth ride from the reviews I've read. The only reason I didn't buy it is because I want a more aggressive drop, and found an excellent deal on coilovers. I honestly wouldn't replace your suspension with another non-sport OEM from BMW, there is just too much body roll and understeer in turns. I should know, I have the same suspension (at least for a few more weeks)
You could buy Bilstein HD struts/shocks, and pair them with a good set of used OEM sport springs. They hardly go bad before a certain mileage, and I'm willing to bet your mechanic is also looking to make a bit of money with you. The Bilstein touring class struts/shocks offer the same daily driven solution as the HD's for a much lower cost.
If you do decide on the H&R touring cup kit, for your OEM non-sport suspension the approximate drop is 1.4" front, and 0.75" rear. (I bet you're sitting lower right now because of your aged suspension anyways, so the difference would be less). For reference, here is a picture of the same car above BEFORE the H&R kit install: