The biggest limitation on upgrades is your 460W PSU.  Your CPU is maxed at 6700k, which isn't a worthwhile upgrade from 6700. Upgrading the CPU or GPU requires a better PSU.  But the cost isn't really worthwhile, especially if you're not experiencing any issues you'd like to remedy. You could add RAM, but keep in mind the next gen tech including DDR5 RAM is expected to come out probably next month. May be better to save for a new system.
I have an Aurora R5 and I was wondering if anyone knew what should I upgrade or what can I upgrade? Bought it in 2016.  These are some of the specs. Alienware Aurora R5 base Intel® Core™ i7-6700 Processor (4-Cores, 8MB Cache, Turbo Boost 2.0, up to 4.0GHz) Windows 10 Home 64bit English  Alienware™ 460 Watt Multi-GPU Approved Power Supply NVIDIA® GeForce® GTX 1070 with 8GB GDDR5 8GB DDR4 at 2133MHz 256GB M.2 PCIe SSD (Boot) + 1TB 7200RPM SATA 6Gb/s (Storage)
Aurora R5, possible upgrades, #2