The earlier 9000s used thompson 40kv tubes and were very problematic. I don't know when they switched to 34kv tubes, but my late 95 marquee 9000 has 34kv tubes. The marquee 9000 is fundamentally the same as the 9500, except that earlier ones have thompson tubes. The 9000 has a 34kv hvps while the 9500 has a 34.6kv? Some 9000s have version 3.4 software, containing all the features of any later software(except maybe fewer internal frequencies and other nice, but unimportant features). 9500's had later board revisions that improved image stability and high frequency performance over the 9000. The 9500's focus module has greater range than a 9000's allowing sharper corner focus. The 9500u is another step above the 9500, but smaller than the jump from 9000-9500. Even with all these differences, with a good knowledge of the marquee, you can make a 9000(non thompson) produce an image exactly like a 9500u, but it takes a lot of time, effort, and quite a bit of soldering.