Re: Old stuff
The PC is definitely worth money, particularly if it has the monitor and model F keyboard. How much depends on the options. CGA will be worth more than MDA, colour monitor more than monochrome. If you've got an IBM EGA monitor that's rare and worth a lot more.
You could of course keep and enjoy it yourself, there are various modern upgrades such as the already mentioned XT-IDE, even a USB storage option(!).
No idea about the Alphastation 500, depends what the collectors out there want for it. There's a few on ebay but I suspect they're more aimed at companies desperate for legacy kit than retro collectors, and they're not selling.