I just reinstalled the game and all the dlc I had purchased, and I have forgotten if it matter if I go after Mahunes (sp) or any special armor or weapons right away? I don't want to go get it at level 1 and have it me useless in a few hours.

THanks

Yeah, if you want the best leveled stuff from the Mehrunes Razor DLC, you should hold off until level 20. More info http://www.uesp.net/wiki/Oblivion:Mehrunes_Razor#Mehrunes_Razor

Most quest rewards are based on the level at which you get the item. They max out at different levels. All max out by level 30.

Daedric quest rewards however always have the same reward -- they are not leveled to when you get them. However you may have a level requirement for starting a Daedric quest.

Vile Lair is a bit of an exception, because those rewards are leveled to the time that you install the plug in, and not when you first visit the Lair. So if you have that plugin installed from the start, you will always get crummy versions of the nice items in the Vile Lair.

One more thing, the Knights of the Nine armor and Weapons are unique in that they will change their level based when the character levels up, if you put them on the stand in the Knights of the Nine headquarters.