I have a pretty good stash of old German made MB Quart car audio speakers. I did a custom install in my wife's G35 coupe with Quart RVF components, and JL Slash amps. Came out pretty solid. Didn't care too much for the RVF tweeter, but I chose it due to the perfect fit in the factory location. Tweeter was a little laid back for me. Sold car.
My preference is QSD. Price is a little high, so I settled on stashing PCE. I have three sets of NIB PCE-216.
PSD would be another superb line, but pretty hard to come by NIB. QSD and PSD was the peak of Quart when it was the original company. Rockford Fosgate owned Quart during PCE, but manufacturing remained the same. QSD, PSD, and PCE all use the same tweeter. It's perfection.
I recommend anyone looking to buy original German made MB Quart products from an auction site to be certain they are buying the real thing, and to only buy a NIB item with returns accepted. The model lines I listed(QSD,PSD,PCE) are considered to be the three best lines turned-out by the original company. There are Qsigs, but they are very rare.
If you don't have the ability to do a professional install, or don't have access to a professional willing to install the merchandise, buy new from a dealer.
JL mids and tweets don't do it for me. If limited to a choice between JL and Alpine mids and tweets, I would buy Alpine. But as I mentioned, I would drive a good distance to get my hands on better products.