Good post, Curtis. I think you should set-up your own auto- purchase advice website and make some bucks off your experiences.
You do mention a couple of things. Mercedes is busy earning a poor reputation for quality in recent years. The ML series in particular is similar to the Land Rover. Resale prices are severely depressed due to chronic, repetitive quality, parts and service issues.
These make attractive buys, but are utterly disastrous to own and operate.
The diesel Merc idea......too slow for the OP's criteria, imo, but a good choice, otherwise. I was offered an immaculate, older MB diesel a few years ago for $2200. Regretfully, I did not take it because it was slow like molasses uphill in winter. But very economical, reliable and nice-handling.
I had not suggested the Town car, because it did not seem like the OP's kind of thing. But, if a Town Car is acceptable, it is, imo the best bang for the buck. Very reliable, very sturdy and cheaper to fix than most others.... but a bit of an old-mans image, though.
I still say the Cadillacs are worth considering. 8K or less will easily buy a very nice 6 to 9 year old one. For the money, these cars are (300 HP) fast and the Seville STS handles pretty well. (The Deville is super-roomy but has somewhat-floppy handling.)
Parts are usually cheap to get, they are straightforward to work on and decently reliable.
They only have one problem..... the cylinder head bolts like to pull their threads requiring a head gasket change and a thread kit. You sometimes can find one with blown gaskets going for a song. Then spend 2k fixing the engine and the engines are good for 300k+ miles. You will still end up with one for half the cost of anything else that's similar.