Tektronix 7603 with 7A18 (for ~75MHz) or 7A26 (for ~100MHz) amplifiers - if you can find one at a LOW price. And you have the room! They made this model for 20+ years so there are a few around. Its also the slowest of the series so prices are not as bad as the others. Avoid the 7A13 diff-amplifiers.
The tubes do not have a super sharp trace but it does have a large screen. Yes, they are absolutely packed with custom silicon but nothing with particular reliability issues. I think the channel switches can be destroyed by hot-plugging (so don't!) and I've had a single failure in a V-out IC. But there are dipped tants on board
Not the easiest things to repair, the amplifier / timebase modules can be a disassembly challenge and the 'backplane' is tricky to get at. The PSU is modular, and linear, though it doesn't exactly fall out by itself
There is usually a fan, but its not shifting a lot of air.
dc