Incidentally there are new meter calibrations with this release of Logic including EBU & IEC-I/II. The IEC--I seems to have the bast ballistics for multipurpose monitoring of levels. You can also set your peak decay times as well. It's best used with the meters set to Sectional-Linear mode... If I recall correctly
No sign of the K-System yet though, but it could possibly be on its way.
Im running a 5k Retina iMac and generally don't have problems with its metering, they are quite clear, sharp and precise but I am running under Yosemite.
But if you are in the market for better metering there are some great meters at Waves.
These are much larger, but also have different calibrations unlike the Logic plugins.
Waves have regular sales so I'd wait for them