Need some advice,

I have a Rampage extreme2 and a Lsi 3 Gb/s, SAS, 8-port Adapter, i currently use this adapter with my two hp 15k sas drives in raid0. I want to upgrade to two 120gb vertex drives and put them in raid0. My question is should i use the on board controller from my rampage extreme or the lsi sas controller.

Here are the specs of my of card
http://www.lsi.com/storage_home/prod...2er/index.html

P.s Will two Vertex drives in raid0 be faster then two of these in raid0? http://www.newegg.com/Product/Produc...82E16822332008

Thanks for the help