sure a bigger skimmer is better but looking at your tank it is not heavy stocked and the rating on the Deltec skimmers are far more conservative than most so i dont think the mce600 is running at its limit in your tank.
A ap600 insump model will be a next size up from the mce600, but A bigger skimmers is nice to have but if you want to save some money other things can be done to improve water quality.
Even with my monster skimmer on my tank i have to do other things to improve my water quality,
Weekly water changes are very good as it exports waste on a regular basis. something i dont get time to do but notice things do better when i do.
I run zeolite, carbon sometimes, 4Litres of rowaphos. runing a miracle mud sump with algae.
But find that when my nutrients get low my algae does not do well. its a good sign of water quality
I also add prodibio bacteria to help with waste removal.
I feed limited frozen foods.
That is why i suggest that water quality is not just about having a bigger skimmer.
A skimmer will remove about 70% of waste but it cant remove the other 30%.
You can put my Deltec ap1004 on your tank and you will not be able to remove the other 30% of waste. But it will look impressive