Hi there Dave. It really depends what is most important to you. All three options are a step up from your popper, but they provide quite different experiences.
I have a Behmor 1600+ and I love it. While I haven't used a Gene Cafe I can't see any reason to buy one over a Behmor. In my opinion the Behmor offers better value overall. It's cheaper for starters, gives you the option of roasting up to 450g batches, has excellent auto profiles and also gives you the ability the intervene in the process with some basic manual settings. If you go for a Behmor make sure you use some of the money you saved to buy a Heatsnob so that you can profile roasts on a computer. In the last 15 months I've done over 100 roasts on my Behmor and am really happy with it.
That being said, if I could afford one I'd definitely buy a Hottop. The Hottop really is the only domestic size roaster out there that mimics the way a commercial drum roaster works (without going further to an Ailio or Huky). It's still not exactly the same as a commercial roaster, but it's definitely closer. The learning curve will probably be bigger for you, but if learning how to use a drum roaster is what you want to get out of it then it's the way to go. Just make sure you get the top of the range B-2K+. It's an extra $500 on top of the K, but if you're going to spend close to $2000 anyway I don't see the point in buying a roaster that doesn't really have manual settings. The B-2K+ has the added features of a slightly higher capacity, a built in bean temp probe, and full manual control as well as auto settings.
So I guess to sum it up for overall value without breaking the bank and good mixture of features, bigger batch size and ease of use I'd go for the Behmor. But for a true entry point into the world of coffee roasting on a drum roaster with manual control and real time profiling I'd go for the Hottop B-2K+. Hope that helps.