I'm thinking about selling my Rig for something that doesn't take as much power, and something thats more subtle color wise. This is my old rig, and what I think it might cost. https://pcpartpicker.com/list/cgVxKZ
The case is much the same - it's probably more useful to you, than it is on the used market.
Rarely do they come up.... if it's in great shape, you might get $100 for it.
The SSD is also similar. While your $90 expectation is reasonable (they've sold used for $120 on eBay)... it might be more beneficial to repurpose it yourself.
So, parting it out and with a healthy does of luck, your range is likely to be somewhere between $700-$860.
If you want to sell whole, chances are slim you'd get close to that. It's unlikely somebody wants the EXACT same setup you have there. They might want t he CPU/Mobo, they might want the GPU..... but probably not it all. IF you were selling it whole, I'd ask $700-$750...... and probably be prepared to take the first offer >$600.
If the case/SSD/PSU are in great condition (which they'd have to be to get anywhere close to top *used* dollar for them), they'd likely be better put to use in your new rig. That should still free up $500-650 from the other components.
Cases are hard to Sell used IMO. SSD can be had for under $30 with Free shipping on Ebay, R9 may fetch $350 plus in today's AMD market. I agree with above you are best to part it out.