You're not going to like my answer but in your situation I would likely go with a Dell Enterprise workstation and pay for their premium tier service.

Something I find interesting is that you say RAID has saved you twice. (You've probably already done this but...) I would double check environmentals at and power quality to your hardware if you've experienced hardware issues with any regularity. Environmental stability and clean power are GOOD. wink
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"There is not a man of us who does not at times need a helping hand to be stretched out to him, and then shame upon him who will not stretch out the helping hand to his brother." -Theodore Roosevelt