I wish I could give the HE-500 better marks. It's had such good reviews; even Tyll Hertsens seemed to prefer it to the LCD-2 (Rev1). It just lacks magic to me. If anything it's made me appreciate just how good my phone is, which I guess I knew but which only a comparison to an equally respected phone can legitimize. I won't even pine for the Rev 2 now; I have a feeling the Rev2 would lose some of the Rev1s special magic. I'm sitting pat.
Actually, if you read the comments of that comparison, Tyll says he personally prefers the LCD-2 Rev 1s to the HE-500s, but that he could see the HE-500s appealing to a larger audience.
Often I get the upgrade itch but every time I put on the LCD-2s I'm reminded just how special they really are.
Bifrost aims at neutrality/anonymity, ie providing no sound at all, similar to (though obviously not as effective as) the highly rated Violectric V800. You'll probably find it a big upgrade, especially with the Lyr paired with the right tubes. Alot of people like the analytical/detailed sounding ESS Sabre DACs with the LCD-2s as well, like the M-DAC or any of Audio-GDs offerings, which may be worth looking into also.