Subharmonicon is a very quirky synth, not just in what it does but in what it doesn’t do. I think you would enjoy your modular experience more if you focused on expanding those gaps in functionality, namely modulation. Getting something that could do envelopes, LFO’s, scale/offset and mixing would push what you can do with the Subharmonicon way further. Maths is a very popular choice for this but if you want to be less “cliché”, there’s tons of options by combining other modules. I would also look for perhaps another VCA as it means you could do create patches closer to true polyphony, as well as more complex modulation behaviors.
I would also concur that Synthrotek is not a good choice, not just because of the controversies but because I’ve seen far too many horror stories of their power supplies being poorly constructed and either not powering modules properly or straight up breaking them.
For a filter, I think you have a lot of choice in Doepfer filters that are all at a comparable price to Behringer. You could also just load a noise sample into the Squid Salmple, so I wouldn’t worry about the lack of noise starting out.
When selecting a power supply what you need to be concerned about mainly is whether the total mA exceeds ~75% of the total power draw of the modules in mA.