Try not to place another "tall" piece next to the fireplace. The 2 visual heights will compete and through the room off balance. Perhaps an all glass shelved cabinet would work, but, it would be best to find a great looking 36+ high chest/cabinet with a mirror or tall piece of art above. They now make faux chests that flat screen TVs sit in and then raise out of when watching is desired. I would try that. It will create wonderful interest and add to the focal point of the fireplace instead of competing.