What? When cycling power, your 3DS won't boot? How exactly did you update, and did the system version say RX-E and NOT Ver. Or RX-S?not quite,my 3ds is dead >.>
black screen after system restore,placed the sd card,lauched rx rools then when i pressed laucn rx...it got black screen of dead. (or whatever)
And do you have a backup of either your sysnand, or your emunand? (You can use emunand tool on your SD card to extract it, if you made one...) if so, you can restore it with a hard mod.