In the US, I think 888 is one of the best options. It's about $100.00, here. Maybe less.
The UI is clunky, out of the box. But you can set up to 5 presets. Once I got used to using presets, I prefer it for consistency. I have an analog 888 from years back, which I haven't used in quite a bit, now. But I do some production soldering. I also cheat, having hacked the interface with 5 push buttons, one for each preset.
Other than the digital interface, the main difference of the 888 vs a 936 is a significant boost in power and a better iron stand. Maybe one of the best iron stands ever made.
Been using the 888 for over a decade, and the only part that has needed replacement is the tip. I've replaced one or two in that time, and probably gone through 5 lbs of solderwire... which is quite a lot of solder for SMD parts.
I paid about $60 on my T12 station and it outperforms the FX-888 in every way.
IMO, Hakko 888 > any T12 clone. I have two T12 clones. Forced myself to use T12, solely, for 2 months just to make sure I got used to it and didn't short change it. (Soldered probably around 1K-2K components in that timeframe). Compared them side to side, extensively. Did actual testing with temp probes. T12 clones do not perform even as well as the 888 in the way that matters... i.e., the T12 clones had to be set to a higher set temp to solder the same things, noticeable after months of use and confirmed with scientific testing with temperature tester. There was more thermal drop in the T12 clones, using the same tips; the T12 stations had to be set higher and had to be turned up higher and/or more frequently when encountering heavy joints, using the equivalent tips. Despite much faster warm up from cold. Marketing hype and placebo effect, IMO; oooh, cartridge! They are pretty good, and better in a couple ways (which don't matter for 99% of people 99% of the time, IMO). In another country, where the price difference is much greater, I might actually recommend a T12 clone for a hobbyist. In the US, there's almost no reason to not get a genuine 888 other than maybe the UI. Cartridge vs T18... not a real improvement for most hobbyists, IMO, or even a pro like me. Not until you get into 100+watt range and/or production soldering (one joint after the other, nonstop) of huge thermal mass stuff.
Real 951? I can't say an 888 is better than a 951. I have never used a 951.
Edit: I did such extensive testing partly cuz of STJ saying multiple times T12 clone >> 888 for 2 months straight. I guarantee he has never used an 888 and probably doesn't solder very much. He posted a pic, and it showed he was still using the fold out tin stand for the clone, lol. One of the clones I bought was the same exact one he raved about, just to see how cool these magic beans were. I'll say for the money, both the T12 clones I bought and used work really well. They can do w/e I need. That said, after my trial period, I haven't used either one in almost a year, now. I prefer the 888 for ergos and better performance. I went a bit overboard, at that time, too. I think I must have bought over a dozen different T12 tips and probably more than half are still unopened.
When you do production soldering one or two (long and boring) days a week, you might spend a bit just to change things up!
When it comes to the "old, obsolete stations," 888 != 936 and 936 != any generic, sub $40.00 Hakko compatible iron.