hardware SAS controller

I am newbie to SAS RIAD. I researched the basic of SAS architecture but I
would like some feedback form real experience as which controller may be
better of reliable and fas data access?


Looking at the traditional Raid 5 vs mirror for data need to be searched
quickly by content.


Used to be using Adaptec controller for SCSI drives and they seemed to
robust enough.
now the intel server does have its own megaRaid SAS controller. Would there
be benefits from upgrading to some SAS controller along with Seagate Hard
drive upgrade to 2x Cheetah® 15K.5 SAS 3Gb/s 300-GB Hard Drive -
ST3300655SS.

what would be a good choice for SAS hardware controller from use experience?

or should I stick to RAID 5 even with the new controller?