Time to move from Boxster - Opinions appreciated

[impboy]

My 2001 Boxster has been just awesome. It's only left me stranded twice in the past 11 years. It's been so easy to work on. I could do a set of brakes in less than 30 minutes with a floor jack which I think is pretty good for someone who's nearly 60 years old. The cost of repairs has been very reasonable. Now I think it's probably time to move on to something else. Since I know there are "car" people here, I'm looking for some direction about what to get next.

Background
I'm three years out from retiring and won't be able to afford to get a new car after I retire on my teacher's pension so I need to purchase something soon. I live in San Diego where I can drive top down nearly 85% of the year so I'd like to get another convertible under 30,000 miles and under $30k. I'm looking for something that my wife can drive, too, and while she can drive stick, she'd prefer to have an automatic. She's not a fan of something as small as a 986.

Knowing that my funds are a bit limited, that I like to work on my own cars, and that I'm looking for a convertible car that will last another 15+ years like my Boxster, do any of these choices sound good? I'm not looking to buy a brand new car, just a late model car with low mileage.

1. Audi A5
2. BMW 228i
3. BMW 428i

Do you have a different suggestion? Thanks in advance for any help.