I already own the system, just thinking of what to upgradeAre the spec listed, is that what you have now and looking to upgrade. If so, I would upgrade your RAM from 8gb to 16gb and add a ssd like cc stated. The PSU is questionable IMO....that series is just the entry level and a bit under wattage for my tastes.The recommended minimum wattage for the GPU is 600 watts. See here. I'd opt for a new PSU. If you like Corsair brand then something in the RMx or RMi series.
I already own the system, just thinking of what to upgrade
Thank you, will grab some more RAM and an SSD!1. Memory (16GB, you have the CPU and GPU power, now you need the extra memory to back it up. However, current pricing makes it a pricey upgrade right now.)
2. SSD (I think the benefits are obvious here. I've been noticing some price drops on SSD's recently.)
3. PSU (550 watts does seem low but if you are not experiencing problems, it can wait.)
If you do all 3 of those, you'll have a healthy PC that should last you a while.
4. MB (Some enthusiasts would say the 7700k is a waste on a H110. But if the board suites your needs, then leave it.)
Good luck and have fun!