If you're open to buying used, BMWs are the best thing out there (and there's a strange correlation between MB diesel ownership and BMW ownership). Check out the K75, a 750cc water-cooled triple, sold from 86-95 in the US market. Jim H is right that the standard version has a fairly high saddle height, but many of the ones sold from 89-95 had a factory lowered seat option that's very easy for anyone to ride. The bike is very smooth, very well made, has decent power and decent handling. If you get one that's been maintained, you can maintain it yourself and it will last forever. It's hard to pay over $4k for one, and with some negotiation you can pay a lot less. Look for a local one in the K-bikes section on the Internet BMW Riders' Marketplace site:
www.ibmwr.org/market/