Excellent review. As I have experienced several "glitches" with the V-Moda amps, I am considering the C5, but I wonder if it would be a step down since the C5 is just an amp with no DAC. How would you describe the improvement in sound through C5 vs. Iphone direct?

Hey there Craigster75! Versus the iPhone's headphone out, the soundstage with the C5 expands both in depth and width so you get a better sense of space in the track. Also the treble seems to be smoothed out and is less harsh/grainy-sounding. The midrange is a tad bit more forward so it's a bit more engaging.
I forgot to mention in the review, but the high gain mode has a slightly different sound profile from the low gain mode. The bass becomes a bit boomier and the treble becomes a bit softer. If you're looking for a less fatiguing listening experience, this is a great option if the higher gain (6.5x) isn't a problem for you such as when you're mobile listening.
I haven't tried an iPhone DAC before, but the difference in sound between the iPhone 4S + C5 isn't much different from my standard reference ODAC DAC + C5.

Would the Objective 2 be a better amp for a Grado SR80? I'm assuming since you say the 02 is not as bright, more laid-back in the treble and with a bigger soundstage than the C5.

I would say yes from a pure synergy perspective. If you need a more portable O2 on the other hand, then I would say the C5 is a good alternative. The C5's brightness isn't a huge difference, but it is noticeable when done in an A/B test with the O2.

Miceblue you ised this with your AKG's you said in your review. Did you think they were driven well? I might get tbis for ther Sennheiser HD 650 and that's also a 300 ohm headphone.