Now that the GOTO's are out, you can probably pick up a noncomputerized used one reasonably. My niece got her 8" Meade from a club member for $500!!
Of course, one has to LOOK for stuff with these. But unless you are really deep into it, beyond 8" might be getting into a diminishing returns scenario. If you visited the above uRL I posted for my 10", you see that I built the 24" at Penn State, and quite a few others. But with the skies the way they have been the last 15 years, you may not gain as much in huge aperture as you expect.
Jupiter in a 24" is a sight, though...