PC build power safety check

Well considering i plan to keep this current setup for atleast 18 month before i change ANYTHING after gettin the 2 new GPU's Im more than likely not going to push the 980 Ti's/"Radeon Fury" past its boost clock. also lowering CPU back to 4.0 as TBH i dont see any improvement by increasing it to 4.4Ghz from 4.0Ghz. literally 0% gains on anything i use my Pc for typically(gaming, streaming, home theatre)

So from my own experience + what my AX860i monitoring software is telling me (while playing GTA V with all setting at highest possible), my current setup according to Extreme power supply calculator, my system should be using upto 480w (not including overclocks) typically when gaming (calculator set to 90% TDP)

However my AX860i dongle tells me im only using 512w even with my gainward GTX 970 @ 1502 Mhz core clock. which im pretty sure is more than the power of what a 980 Ti would use on a standard boost clock that some1 like ASUS or EVGA would assisgn along with their custom cooler on the GTX 980 ti.

so with a MAX TDP of 250w(standard PCB also) on 2 cards, max 88w TDP on CPU. and the rest of my components plus i dont plan on overlocking on allready boosted cards, its safe to say i would be under the 700w mark? which is what im aiming for as i think a 100w - 160w headroom while underload is safe.

On another note
when on idle or less demanding games which i do tend to play alot of LoL, WoW, GTA V and the odd not so high end games here and there, i wont even reach the maximum wattage on my PSU or the max TDP on the GPU's, as i run games with at most a 144 FPS lock if possible as anything above would be a waste due monitor limitations.

With that logic which i hope is considered somewhat reasonable, think it would be fine? as i would like to avoid gettin a new PSU If possible while still gettin 2x Radeon R9 "whatever the hell AMD calls it" or 2x 980 Ti.

any1 care to elaborate or condemn me for my logic? as much as i dont wanna buy another PSU (as i bought the AX860i like 2-3 weeks ago) i dont wanna cause any harm to any of the components dispite corsairs anti-surge/overvoltage/undervoltage protection within the PSU.