I wouldn't fret too much about these ending up in a drawer.
The Siglent is a great option for $400, and probably the better choice right now for a low cost but fully featured oscilloscope. If you had a $600 budget, I would probably buy that scope and a cheap/used PSU, DMM and soldering iron. Then save for a cheap Feeltech or Uni-T AWG.
With your budget, I'd say the Analog Discovery is the least likely to end up in a drawer when (if) you upgrade your lab. Don't be too impatient, you'll get there, and components, prototyping boards, consumables, and cabling really do add up.
As for the HANTEK, it's actually more capable generally speaking than an old CRO, and you can get it often cheaper than a working analog 'scope. I don't have it, so cannot recommend it, but I doubt is as bad as people paint it.
An analog oscilloscope might be a good option if you'd like the puzzle of a repair and find one for peanuts. I was defeated by a tek 466 with HV problems, and a more modern Hameg, and then too budget-strained by a Tek 2465 which I troubleshot correctly. Take that for what you will, but $100 on an old boat anchor might very well leave you without oscilloscope and $100 poorer.
In any case, the AD3 is a real tool, actually useful, and will remain as such within it's bandwidth and input limitations. It's not a direct competitor to the newer Rigol and Siglent lineups.
The third option presented by some other users is also valid: save for standalone, fully featured bench tools from recognized brands. It's your choice at the end of the day, but I would personally get the Analog Discovery unless you can gather $800 in a reasonably short term to get a basic bench.