How many watts should I use?

How many watts should I use for this the P.C. I'm building. I got the G.P.U. for VERY cheap, but I do plan on upgrading within a year. Most likely a 780 ti or slightly better. Please take that into consideration. Id also prefer not to max out the load on the P.S.U. Maybe 80-100 watts over max load. Thanks for your feed back. ☺





C.P.U.- Intel i7 4790k 4.0 ghz

Motherboard- MS-I Gaming 5 Z97

G.P.U.- GTX 660

RAM- 16gb (4x4) ddr3

Storage - 500gb Samsung 840 Evo SSD, and 500gb Seagate HDD

1 DVD-RW

Fans - 4 120mm case fans

How many watts should I use?