Some say that part of Jimmy Page's sound lies on the use of an Echoplex EP-3. Fewer know that this tape echo was renowned not only for this particular effect, but also for his preamp stage that tailored the sound of the guitar. Considering the size, weight and cost of this piece of gear, it doesn't seem reasonnable to search for one to grab. But in a pedal size, you'd be a fool to miss it!
This boost will have a tendancy to enhance highs without getting harsh though. It is so recommended for dark sounding configurations to better cut throught the mix.