In my game I have used the circlet (as helm), AT 13 to AT 14, AT 13 to AT 17, as well as many others and it worked fine. But my game at the time was not really a low powered game in that the PC's tended to find stuff much more powerful than could be created at the time.
My games tend to stray more toward gritty and low-powered. Most of the powerful magic items characters find do have downsides to them.
My games tend to follow along the same routes. But, I should have mentioned that the tiara Sara wears was actually manufactured for her great great grandmother many hundreds of years in the past and has been handed down through the years. It was with Sara's grandmother being killed, but a companion returned the tiara to her family, given to Sara's mother, and the knowledge that the tiara is magical was lost. Sara only wears it as an heirloom and still has yet to discover its magical properties. She only thinks her combat dodging capabilities and her own Power usage is what saves her from many blows that should have killed her.
However, whenever Sara is near a ManaNode, the jewel in the tiara begins to glow brighter the closer she is to the Node; thus, that could spoil her Stalking and Hiding. She has noticed the jewel does glow at times, but still does not know what it means.
Thus, in a way, due to the massive amounts of Lore lost over 1300 years ago, you can say such things do have a kind of downside. Sometmes horrible, sometimes with no consequence.
Sorry for the ranting. But as many have said, and
I do agree with, it is all dependent upon how the GM defines how magic/power works on their world.
rmfr