Apparently the "Sage" (which is what I have currently) has a quad-core, but Kobo discontinued it. Sigh, too bad - this was my favourite to-date (needs a power-cover though...).
Off topic, but I don't understand Rakuten's current product strategy. They discontinued their two best devices: the 8" Sage and the 7" Libra 2. What's left are two unfortunately sized B&W readers (the tiny 6" Clara and giant 10" Elipsa) and a couple of color readers that no one should buy unless they absolutely NEED color (I've tried them, and the screens look terrible compared to the B&W versions).
I have Kobo Sage but it's not a great device.
Very bad battery life. Maybe 8hrs of reading with wifi off, BT off and only low screen backlight. I need to charge it daily or every other day at best.
Physical buttons are comically bad and often don't register presses.
Built-in book reading app is slow, lacks some critical features and hangs in many epub books. I replaced it with KOreader which finally made the device usable.
It's a great screen size though (9" would be even better).