1.Is this a decent build?
2.What should I upgrade in it?

-Asus Z87-A
-Asus Geforce GTX 650Ti
-Kingston 8GB DDR3 1600MHZ
-Cooler Master Thunder Mod 620Watts Power Supply
-Liteon IHAS-124 24X Sata Black DVDRW
-Intel Core I5-4670K (3.40GHZ) 6MB/4Cores/4Threads/4600HDGFX/22NM LGA1160 Processor
-Cooler Master Case (Forgot Details)