earlier today was only 3 left (no deal), but now more than 10 in stock. $50 off with coupon.
Lowest price I have ever seen it.
it looks like a planet/ball but it's more disk shaped. https://i.ebayimg.com/images/g/q3IAAOSw8klhjgKU/s-l1200.jpg
I know someone who has Onyx 5 and they are very happy says it's well designed.
image of drivers: https://i.ytimg.com/vi/nxgI9aoDaZo/maxresdefault.jpg
yes you can connect two together "Wirelessly connect two Harman Kardon Onyx Studio 7 speakers for an elevated music listening experience."
Pro's: sounds great, interesting design.
Con's: powered by single 3.7v cell. max battery life = 8 hours (more like 2 to 2.5 hours at loud volume probably). sounds better when charger is plugged in apparently.
also if reddit post is anything to go by, Onyx Studio 7 has much richer sound than Bose Soundlink ii which I think was popular on ozbargain. also vs Soundcore Motion+, Onyx has more bass but Motion+ has more clarity.
a comment says with heavy use older Onyx battery which is single 3.7v cell like Onyx 7 battery conks out in about a year (makes sense given how tiny it is = more full cycles) but it still works plugged in.
it went on sale in the US for $150 ($229AUD) so this is a good price to consider it.
also currently $299 at Telstra. not sure if you can buy it with points though.