For people who missed the sales from Computer Alliance due to out of stock, found this link from Futu Online Ebay also selling at the same price once you select "4 Bay DS920+ 4GB RAM".
If you also wanted to by the HDD, remember there's a promo run by Seagate you could claim $60 e-gift card if you buy 2 x 8TB Ironwolf (different amount for other sizes)
https://nbg.seagate.com/anzpromotions-IWPromo
Enjoy!
A new one of these comes out about every 2 years. It is a great deal, but just be aware that a newer model might be just around the corner, hence the discounts.