Gonna probably buy it next week, I'm very close, 90% of me are fine with it

How much would you think I could sell my Qnap 659 Pro II with 6x2TB disks? I only find prices of the newer model, the 669 Pro, but it seems to be almost the same, and it is 900€, although the disks I have are not available anymore, but on my bill I can see that they were just 62€ anyway 2 years ago. My NAS was 1100€ with the delivery.

I could get the 2413+ here in Luxembourg for the same price like in the German online shop where I always order, but the disks are 7€/disk more expensive. I want to order 13 disks, to have one spare one from the start. I mailed the shop in Luxembourg if it would be possible to get a little discount on the disks, hopefully they will agree. On the other side, I wouldn't have to pay for delivery, as I could pick it up from there. Probably they also have everything on stock, so I could get it straight away, although they told me that it would be ready in 2-3 working days.

The other problem buying it online is, that I would have to send the money via bank transfer, as it will be almost 3000€, and my VISA limit is quite lower, and with the bank transfer, you never really have 100% guarantee, because if the money gets lost somehow, you're not really able to track it, and see if the seller didn't receive it or not, so I prefer to not use that method.