I would at least try the retail hsf....for most heat doesn't stop them in their oc endeavors...it is likely stability caused by chip liitations, vcore adjustment abilities, and often reluctance of users to go so high in tmeps and vcore adjustments....
I had a retail unit with hsf and I ran my
1.8@2.4...the temps were at 60c under load, but I really never trusted the accuracy of the msi board anyway...through it on my asus board and had much better temps...spent 20 bucks on an avc hsf and it only helped the temps fopr me by about 2-3c idle and 5c load....but the asus board measured temps at 36-38c idle and 48-50c max load of prime95 for 12 hours...