First 200L is ~52 gallons US. I need to know the readings you have now. I am a perfectionest too so "a bit up" doesn't make any sense to me. Please give me some #'s. Your water Parameters will tell you how far along you are with your cycle and when it's time to add life to your tank.
A sump is a good thing for a couple of reasons.
1) more volume of water and that is always better to keep your tank stable.
2) it hides all your equipment...heaters, skimmers, refug. more LR
2) I'm not sure of your layout but if it's an all in one unit it may be hard to add a sump.