There are plenty of ways you can prove ownership, and there are ways you can use the escrow services of established members of the forum and still protect yourself. Ask for signed messages, take photos of the items you are about to ship with identifying, hand written notes with your username and the shipping labels. It's very easy to prove you've shipped the items, if the escrow provider doesn't send you the funds that's wire fraud.
I've seen your posts offering hosting services, and I wish I had seen this post earlier. I was in Portland for a couple of days last month. I'll likely visit again next month. If you're still offering stuff for sale, I might buy a few GPUs from you. Also, I'd love to see your hosting facility, if you're cool with that.
I believe you that you have the goods, but try to have a thick skin about the comments in this thread. There are so many scammers on this site it's to be expected that folks are skeptical. To be honest, even though I believe you I would not trust you enough to send funds without escrow.
Just my two bits, for what it's worth. Good luck with your sale.
ETA:
Here's a post of some guidelines that will help you establish legitimacy:
https://bitcointalksearch.org/topic/posting-guidelines-for-wts-physical-goods-marketplace-4576802
Here's a list of trusted escrow providers:
https://bitcointalksearch.org/topic/recommended-bitcointalk-escrow-services-2439910