My advice: don't sell it. You'll never get the price you know it's worth in your head. Unless maybe if you're willing to pull it apart entirely and sell every item separately, but that's a lot more work and even then you won't be sure the effort will be worth it in the end.

I doubt you'll be able to sell it for more than $200-$300 as it is now, and I'm pretty sure it's worth more to you than that. So don't sell it. Give it a second life as a server or an Unraid /FreeNAS box or something. You'll get much more value from it that way.