Decided to mess about with my LD I+. So far I changed from stock to CV4015 EF92 M8161 9D6 MULLARD 8114. They sound pretty good with ah-d2000's so far. There's bit more clarity and bass seems to be fuller. They do heat up more than stock tubes though.

I should probably add few more details, Im using LittleDot I+ amp and occasionally e17 when Im on the go, or letting tubes cool down. In UK price for Hifiman HE-400 seems to be pretty much double of Denons, however some comments coloured them as more of a side-grade.

Hi guys, Im wondering if Hifiman HE-400 is a decent upgrade from Denon ahd2000's, or its more of a side-grade? I am pretty happy with the sound of Denons, but want to explore something a bit spacey.