Question about belt and necklace

Should i replace my necklace and belt first or save up for a bit later and replace my chest instead

This is my Armory: http://www.wowarmory.com/character-sheet.xml?r=The+Venture+Co&n=Alazlam

This guild should help you out a lot
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Hinata - 80 - Arygos

LF Guild

I don't really understand what your question is. Statwise the epics are clearly better in every way than the blues.
The neck takes the blue and makes it better in every way but a lone point of strength.

The belt is also a lot better but gives you truck loads of avoidance over some block value.
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If it is weak, kill it before it gets stronger. If it is strong, weaken it.