HF2 is a special edition done for Head Fi and TTVJ.com. It's above the 325i for sure. Some compare it to the RS series, and like it better, but I never heard those.

Vs the 325i, which I've since sold, the great highs/mids are there but it's more tamed, not as fatiguing in a good way. There's also more bass and WAY more soundstage. Only 500 were made so the used prices are some times ridiculous. MSRP is $425 but I've seen some in Europe already sell on ebay for over $1K US. Crazy. And these were only shipped a few months ago.