Is this light just as bright on one 18500 as on 2 rcr123

[Isthereanybodyoutthere]

Ok ,i have bought this light for my dad http://www.dealextreme.com/details.dx/sku.10637
But i need to get a charger + batteries for it
I have found these
http://http://www.dealextreme.com/details.dx/sku.936

http://www.kaidomain.com/WEBUI/Produ...spx?TranID=936

http://www.kaidomain.com/WEBUI/Produ...px?TranID=1579

Funny thing is that the cheaper one from Kai has the car dc cable as a extra

Does some one here know if this light will be just as bright with one 18500 as 2x rcr123
Has been thinking of buying some 123 + some 18500 ( i use 123 ,,then if i have forgotten to bring along some 123 i know he has some )

Im in Denmark ,,so i will buy from Kai or DX sins shipping from US would kill any deal i might find there :shakehead or is there any other with free shipping at the same price

What is the best at Kai/ DX for batteries ,,trustfire or ultrafire ( i know it better has to be protected )

Ps ,,i think i have become infected ,,i have made my brother buy a Kai buckle light and a b6 ,,and now i have bought a sku.10637 for my dad