SonicExplorer
I'm on XP and staying there. LoL
If you find an OS version you really like, and have all the DAW tools you need, then just make backups of everything to be sure you can always rebuild a machine if needed. I just did this recently - 100% brand new parts except for the motherboard. Had very little issues except for one wrapper component that wouldn't run in multi-processor mode correctly and caused me a lot of headache to track down. But that aside it was LOT easier than rebuilding a whole new DAW using the latest OS version and having to repurchase a bunch of new software, etc. And worst of all, having to re-learn it all. Not to mention spend a ton of time stomping out bugs and glitches, always wondering if you'll ever really be able to get everything working smoothly. Uh...no thanks, not for me! I don't know how you guys do it frankly. If I kept updating operating systems and plugs and host software and drivers and hardware there's no way I'd ever get any real work done, and I'd be spending a fortune in the process. LoL
You guys can poke fun at me all you want, I'm staying on XP with my trusty RME interface.
Sonic
I sympathise with you here, as the move from X1 to X3, and then to SPLAT was VERY expensive for me.
I had an Win 98 system running 2 x Yamaha DS2416 cards with Pro Audio 7. I'd used on a Cirrus 166Mhz with 128Mb RAM (which could easily cope with recording 16 simultaneous tracks).
By Sonar 3 I'd gone through Windows 2000, to XP with an Athlon 750 with 1.5GB RAM (which coped with 32 simultaneous tracks) and finally a dual core Athlon 4000 with 4GB RAM.
I hardly ever used plugins during this time, as the two DS2416's more or less had everything I needed: 48 channels with dynamics + 4 band fully parametric EQ on every channel, and four effects processors.... and all my synths were hardware.
For X3 I moved to Windows 7 which meant getting a newer motherboard that would still support my DS2416 cards. I opted for the Asus P8B75V with an Intel i5 3750, as this has 3 PCI slots that fully support the voltages needed for the DS2416.
The move to 64bit meant replacing my DS2416 cards with my Focusrite 18i20. At this point my machine was fast enough handle all the mixing & effects in-the-box, and I've just recently retired all my hardware synths.
Many a time I've looked back at how much easier it was when all I had was my Yamaha MT8X 8 track tape recorder, Music-X on the Amiga for MIDI, and a PPS-100 for MIDI tape sync.
I'm still on the fence with Windows 10 vs Windows 7.
Windows 7 has been rock solid (with the exception of the flakey windows update system), just like XP was. To be honest, I know Vista got a beating but I used it for 10 years on a development laptop with no issues. I never tried it with my DAW system though.
I really like using Windows 10. Updates are far more reliable, but it's a real PITA when major updates come along - i.e. settings reverting back, having to re-authorise software. It does FEEL snappier to me though compared to Windows 7, so I tend to stick to Windows 10 with Windows 7 as a fallback.