Arturia is offering their V bundle (6.0) for $249 through December 5th. I think these were $399 last year and absolutely worth it. I don't generally like soft synths, but after downloading the free trial versions I was buying the full package the same day.
Buchla Easel, polyphonic Arp 2600, polyphonic Moog modular, organs, an Oberheim, CS-80....if these instruments were physical units, they'd probably cost you in excess of $300,000. The interface is really good. It's incredibly easy to save sounds, organize custom patches, and then to edit and resave them. ---I will warn you, though, that the modular engines can hit insane frequencies that could damage your hearing or your equipment.
https://www.arturia.com/black-friday
If you want to run your soft synths externally into effects or amps, a simple passive reamp for $100 will get the job done.
https://www.sweetwater.com/store/detail ... ing-device
I had always wanted an Easel, before they were even reissued. That was a bit of a dream fulfilled. The most surprising part for me was the CS-80. All you ever hear from online demos is people trying to do brassy sounds and pads. The software version gives you so many more possibilities---bright, exotic sounds---dark, cinematic soundscapes---vibrant arpeggios.
Even if you only want to use 3-4 of the programs, it's definitely worth it. I bought an Arturia Keystep to use with it, but there are certainly many options in the $50-100 range if you just want a simple MIDI controller that never leaves your desk area.