The Intel IOPS333 was OK back in the dark ages, technology has moved on somewhat since then
The 3ware 9650SE-8LPML should do better than the Adaptec BUT you are limited to <2TB as the Adaptec is too ?
If this is not an issue then give this a try, its designed to run RAID6
If budget allows get your self a LSI9260/65/66 based RAID controller.
2TB+ no probs
Min 512MB cache
Can handle RAID 6 with ease
OEM versions can be cheaper but lack LSI version standard features (ie IBM M5015 needs a key for RAID6)
I was lucky and got a real cheap Advanced feature key (RAID6/encryption) to go with my IBM M5015 with BBU.
All up was $250 included cables as well of Ebay