Best additive for WC loop???

[G-Dubs]

I've managed to get my hands on some distilled water for my first attempt at water cooling, but would like the forums recommendations on the use of additives and silver Kill coils

Are they really necessary and which are best?

 

[G-Dubs]

I've seen the PT nuke, and also the PHN version for a few pence more. Which should I go for do you think.

Also looking at which thermal compound to go for on the CPU. Previously just used whatever came bundled with the airheatsink.

thinking either Arctic cooling MX3 or MX2 or the arctic silver 5, but open to suggestions