To flash AHRD you will have to have a unlocked bootloader, either by HTC Dev method or by Revolutionary method. Now as stated by you, malybru, and myself we all know Revolutionary is not compatible with Hboot 1.27.0000 (as of right now), which your device currently has. So this leaves only the HTC Dev method. Now I personally agree with others here on XDA, I would normally stay far away from unlocking via HTC Dev. But seeing as you bought your Sensation new with Hboot 1.27.0000, you really have no other alternative but to wait for Revolutionary to update or for some other means of unlocking becomes available. Also if you do manage to downgrade your Hboot you will have to use HTC Dev to do it.
Now I am in no way saying you should use HTC Dev, nor am I advocating HTC Dev. I am just trying to inform you. What you do with your device is your choice and your choice only. But what ever you do, please post back here with your decision and if applicable any results.
Also if you was wondering why you have to use HT Dev to downgrade Hboot, read
this post. Yeah I know it is for GB ROMs but I imagine the same probably holds true for ICS. I mean it is the HTC Dev unlock that allowsyou to downgrade in that senario. But what do I know.