I know the part of not wanting to toss something that still works. Guess that's why I still have a working Harris 286-20 stuck away around here.
I give away systems too, upgrade other people's systems with leftovers from me, exchange complete systems, CPUs, memory, videocards, etc.

Casings come and go too, my last new one was a Corsair Carbide 300R. Local hardware store only stocks A-Open, Antec, Coolermaster, Corsair and -since a few weeks- Fractal Design,
but some kilometers down south (Berkel en Rodenrijs, Ridderkerk) there's a whole world to choose from. The only problem is money...