Being one of the best, the L3 is expensive ($700 vs $100 for the O2), and according to NwAvGuy, nothing can beat his O2!
Here are his words:
"WHAT ABOUT THE SOUND QUALITY? The O2 compares very favorably in listening tests against the critically acclaimed Benchmark DAC1 Pre’s headphone output. An O2 user has compared it to a $1000+ AMB beta22 (b22) and wasn’t sure he could hear any difference. I will be encouraging blind listening tests against other gear as well."
I am building an O2 and I will compare it with my LISA III.