seems like you like bmw, which is a great brand with proving history of excellency; you also like a diesel engine, again, a great thought (don't think i don't like diesel - i do and i have three of those, love it).
what i really want to tell you is - diesel for car is an evolving technology, it's getting very complicated nowadays, not everyone can build a diesel car with same quality. in auto industry, there used to be three well known diesel powers - mercedes, vw and volvo. ever since ford took over volvo, their diesel car line was dropped. in current world, there are only two left over - mb and vw.
just like any other technologies, diesel design and manufacturing have know-hows, needing real world tests. both mb and vw diesels have been in market for more than a century, how long has bmw started to make it? zero. bmw realized that there is a big piece of pie in diesel, so they stepped into it, now coming out a diesel version of their line.
do you want to be a donor patient to be in surgery room where you are aware of one of the resident doctors being the surgeon operating on you? Nah, you don't.
With that amount of money, you can almost buy an e320 cdi from mercedes, not mentioning the less expensive of vw's. think it again and be good!!