I also fall into the classic cars/classic bikes overlap category. While my tastes in bikes fall mostly with the Italians, my budget dictates German as the country of choice for my collection of classic cars. I have had a number of Porsches over the years, currently a 1989 C4 and 1968 912. I also love old VW's and have a '61 Beetle Convertible and '64 Karmann Ghia.
I am also a classic motorcyle nut, with a 1953 BSA BB34 500 Gold Star, a 1960 BSA DBD34 500 Gold Star, 1969 Triumph Bonneville, 1975 Ducati 750 GT and 1974 Benelli 650 Tornado.
Bicyles are very easy to collect, as they take up the least space. They are easy to work on, and can be brought into the house for winter restoration projects, which drives my wife crazy.
Bicycles are also healthy, as I not only Research and Restore them, I also Ride!!