OPA2107 is definitely my favorite opamp for the Go-Vibe, followed closely by the AD823. The OPA2107 gives good detail with great bass/lows, and they say the sound signature is similar to the OPA637 (though not quite as good) but at a fraction of the cost. It's a fantastic all-around opamp, even more so than the OPA2227.
From Analog Devices, I actually prefer the AD823 with my HD600s over the AD8620. I find that the AD823 gives slightly more detailed highs than the OPA2107, but without the occasionally harsher nature of the AD8620. I switch from my Senns to Etys, and I find Etys + AD8620 is a bit much, but the AD823 is a perfect compromise.
I have tried the OPA2132, as well as several others, but they were not as engaging as the OPA2107 or the AD823.
Edit: I thought I'd also mention that the OPA2107 does an excellent job on battery life. I could squeeze in a few more hours it seems with the OPA2107 than with some of the other opamps I've tried. It's a fine opamp, and I definitely recommend you to check it out.