I was too was aiming to get Tiptop's Forbidden Planet filter but then I spotted the Omsonic limited run of their (FLF) Funky Ladder Filter which is like the Steiner Parker filter but with extra control, its a very nice sounding filter and very usable. You can mult your signal and feed all inputs then tweak the levels for each HP/BP/LP, you could do this with a simple attenuator and the Forbidden Planet filter too.
https://omsonic.co.uk/product/omsonic-funky-ladder-filter-le-8hp-edition-fire-sale/
The other thing which I think should be a personal toolbox item is the Rebach VCF-AB, its very affordable and if you like the occasional dirty 303-style acid line then this ticks the box cos it will squeal like a distorted 303 because of its internal feedback path.
https://rebach.eu/catch-series/
I'm very tempted by a Stereo Ripples filter and a Patching Panda Moonphase.
Kinda tempted by the ADDAC604 as its double the same filter that they made for their ADDAC105 4-Voice Cluster, which I found more useful than the 4-voice cluster with the ability to feed it external signals, it was simple and workhorse-like, kind of set-and-forget or just throw a little modulation at it for a background element. So with the ADDAC604 being able to be used as a Dual Mono or Stereo filter its quite a good price to keep the Stereo path from other modules, it won't be too crazy but it will be very usable.
https://www.addacsystem.com/en/products/modules/addac600-series/addac604
Enjoy your spare HP, don't rush to fill every last space, this is not like filling sticker books. Resist the urge to 'complete' your rack, its never complete so just relax.