I'd say not to go overboard at first, and address the problems if they become problems. Certainly the comfort mod will be money well spent - but beyond that, a simple mat on the floor can be all you need to ground yourself away from walls.
I personally wasn't happy with the earbuds, and upgraded to wired IEMs which made a huge difference for rhythm games which are music focused, and also made RE games a lot more scary sounding lol. But other than those couple things, I didn't feel I needed much more. I don't really have the space for a ceiling feed system for the wire, but that sounds pretty cool, but then again I didn't really find myself wanting to turn too often in my standing gameplay, mostly 90-180 degrees temporarily then return back once the action cools down.
Edit: Like I don't even know if you'd want to use the headset mod initially, even, until you've learned how it feels/moves around without any additional straps, so you know the issues and then can also understand the difference in comfort when it's added.