I have always had and appreciation for SP regs.... MK-5 & MK-10 garage sale finds when I started 30 years ago. Added many (MK-2, MK-15, MK-17, MK-20/25), and then started collecting vintage models (MK-3). Along with those are a whole stable of seconds. The 109/156 was what I started with, and really enjoyed them. Added the G250 to the collection when I could find sweet deals (G250/250Graphite/G250v). Also ended up with some others (G250HP, S555/600, G200b), then started into vintage (Air1, Pilot, and 108HP). Still have Air2 units from my early days too (2nd thru newest generation). Wife has a 4 generation as she still wanted one.
Honestly, there regulators are great! I do all my own service, and source "black market" kits when needed. The only other SP stuff we have are the Wife's old BC, some gifted BC's, and some Jets (camo edition), and an odd mask. I used to frequent SP shops that were here.
I wouldn't buy anything new, nor would I likely buy any other gear except used regulators.....
YMMV
(FWIW - I also have HOG, Deep6, Poseidon, and a bunch of DH regs (Kraken, USD (modified), Voit)