Both the Energy Link and the Quarry have internal storage, but the Quarry's is in buildcraft's energy unit, MJ. You can basically ignore it though, as it's not a big enough buffer to keep them running for long without a constant source.
ANYWAY, so the Quarry will run at full speed when consuming 9 MJ/t.
The conversion rate that mod uses is 5:2, but the energy link has a bug which means it loses 10%. So the conversion is EU * 2/5 * 0.9 = MJ.
32EU/t * 2/5 * 0.9 = 11.52MJ/t - full speed quarry
If you rearrange the equation, you can find the minimum EU/t needed is 25EU/t. But since there's no convenient way to throttle current from an MFE to an exact value like that, I'd go with 32 =)