Cable extenders

[Terrabytez]

I am looking to replace my current case with the black and red NZXT H440, but I have a few questions.
1) Are extenders safe to use?
2) Anything else that would be worth it to get while I am at it?

 

[Terrabytez]

Please don't post screenshots of shopping baskets from competitors or auction sites.

Sorry about that, I didn't think OCUK sold them, but as it turns out I was wrong.

 

[Terrabytez]

Although I will be able to, I just wouldn't feel happy about doing it. I would probably do a good Job but would find something wrong somewhere.
But the main reason for extenders is that With my current case the cable management is limited and there is no windows so i'm okay with it, but with a clean H440 I don't want to see the rainbow of a CX 600W PSU.