Hi Nathplummer. I see your post is nearly two weeks old, but if you're still interested I'll try to help.
Put simply, yes both Grado and Beyerdynamic make excellent headphones. Which you'll prefer is really down to your own taste. I can't comment on the Beyer DT770 specifically, but I have a pair of DT990s and a (borrowed) pair of Grado SR80s and I couldn't place one over the other in absolute terms. The Beyers are slightly warmer, with a punchy bass response and make for an exciting listen. They're also a higher impedance (at 250 ohm), which makes them an easy load for my integrated amplifier's built-in headphone amp. The SR80s sound lighter and more agile, and seem rather more accurate than the Beyers; but my amplifier struggles with the low impedance and, as such, the sound tends towards shrill and unpleasant. Not the case with my iPod though, where the Grados really sing. I gather that if I had a decent, dedicated headphone amplifier then the Grados would win, but that's conjecture at this stage. I also find the Grados more comfortable for long listening sessions - the Beyers are a bit heavy and can make my ears sweaty!