Most of the Tektronix solid-state oscilloscopes are good instruments to have. I would stay away from their earliest solid-state machines, the 453, 453A, 454, 454A and 422 simply because they won't be as reliable (age) and parts will be harder to find. There are probably more 465s out there than any other scope model from any manfacturer. The 475 is also a good choice. Although the 466 (or the 464) will give you mesh storage, if you ever need a new CRT for the thing, you'll be screwed unless you can find a decent hangar queen. The storage models require more depth on your bench than the 465, but are other wise (except for the storage controls) are identical in every other way to the 465.
The 7000-series is also a good choice, often being not that much more expensive than a portable, even with the plug-ins. Note that if you do get a 7000-series mainframe, you'll need at least one vertical preamp (7Axx) and one timebase (7Bxx). The mainframes offer a heckuva lot of options with regard to vertical amps, timebases, digital counters, logic analyzers, spectrum analyzers, etc. so that you can really expand the scope to do what you need. The mainframes are available with bandwidths anywhere from around 60 MHz (7403) to 500MHz (7904) or even 1GHz (7104), although I'd limit myself to 500MHz must because the 1GHz option is more expensive, harder to find and more difficult to maintain, etc.
Dean