I suggest a later Nikon SLR with a 50/1.4 D-af should be at or under $400. F4s/F100/N90/F5 if you shop well. A cheaper lens which is very versatile is an old 55/3.5 micro. The F4s is sort of a unique bridge between knobs and controls of old and LCDs and buttons of new. The pro bodies have the greatest backward compatibility with lenses.
The Olympus system is also nice, but not nearly as many choices or technology as Nikon/Canon. If you want older small manual focus gear and compact size, it's a good system to be in and is much nicer to use than a pentax k1000.