Unless you want to set your wallet on fire with upkeep costs, avoid the 928. Beautiful, fast tourer but they are hideously expensive to maintain. www.rennlist.com and the 928 board. All you need to know about these cars.

I have never driven an Alpina but that spoiler is naff IMO, as are the graphic strafes all over the side of the car. I would go for the M5 personally, my 3.6 is the best car I have ever owned thus far [which includes 3 911s, a 356, a 968, an e46 M3, and an e46 323Ci]. The M5 is not exactly cheap to maintain, but much less expensive than a 928 I can assure you.