Not sure exactly. I've listened to the HD660s in an AV showroom and loved them (although with "Truebass" turned on on a iFi Zen Dac V2). I plan on listening to the Sundaras next week.

I liked how colorful the HD660s were - everything was loud and clear, very little being recessed when anything else is playing. Not entirely sure how to describe it.

I'm only considering buying the sundaras if they manage to sound better, I guess. From what I've seen and heard, I already fear the comfort, the cable, the QC and honestly I don't really like the way they look. Considering they're about the same price at the place I wanna buy them from, it's gonna be a hard decision.

So, I'd like to know how you thought they compared and (even if) sundaras are worth getting over the 660s.

I honestly don't think so. Listening to music at that volume indicates that your laptop has more than enough to power the headphones. Sure, the circuitry is inferior to a standalone dac/amp, but I don't believe the difference would be that noticeable and your ears will adapt anyway.

If possible, buy one from a place that has good customer service and return it if you don't think it's worth the money. I've solved many curiosities of mine this way.

Thank you for the complete answer. Will definitely put them in the "should try at some point" bucket.

Do you still own the CRA? Would the Chu be an upgrade? I'm kinda skeptical with all the people saying their pair had such a short lifespan.

Have you tried HD660s before? I am TORN between those two.