I dont know enough about people's experiences with crackatwoa. Mainline ought to be an upgrade for sure. I was considering the Lyr2 once, but eventually went for Bottlehead SEX. I made a review recently which can be found on the product showcase page. I'll try to provide relavant info and why you should consider the SEX. SEX has a remarkably neutral sound and FR goes quite low, satisfyingly high, and linear as well. I actually preferred the SEX over Mjolnir 2, overall, for powering my trusty 300ohm Sennheisers (HD650). They also had particulsr synergy with the HD700, bringing out the best of it's sound. With the Focal Utopia, SEX won me over vs Mjolnir (but Mjolnir was slightly better with the Clears, because they love that extra upper treble air). Here is a "very low-quality graph I made," regarding the tonal balance of SEX and Mjolnir compared. (exaggerated and not to scale) Perhaps you can extrapolate this to info about how the Mjolnir compares to Lyr 2. For technicalities overall, I'd score Mjolnir a tiny bit better, but it could be due to the extra "u-shaped," tonality (which is very tastefully done, mind you). Nonetheless, SEX is a single ended triode design. There will be inherent differences between it (other Bottlehead amps), and hybrid designs like Lyr and Mjolnir. It is difficult judging how good an amp is in regard to synergy (perhaps the most important aspect of all). I hope this helps someone. Best of luck in your search.