There have many types of 200w mod recently,for example,wismec rx 200w,wismec DNA200w,and cacuq 

Worldwide Exclusive Distributor For DX DNA 200W,

I recommend the  DX DNA 200W,because :

The mod chip is dna 200 which is stable performance,and have 3 battery option, 900mah lipo/1300mah lipo/2*18650 battery ,the mod have good touch lacquer layer,hand feel very comfortable when hold it,really a high-end box mod.