I understand, you mean the foam surrounds have been replaced, meaning the drivers are 15" HPD's. A common occurance with them. I had mine converted to hard edge surrounds, as in the current Prestige line, by purchasing new cones, and having the conversion done in England.
I hope, for your sake, you are able to get them, they are such good speakers. At one time, I powered mine with an Aragon 3002 (300 Wpc), and they sounded great together, so I expect your 4004 to be a good match as well.
My favorite amp now, is an SET 300B at 9 Wpc, which shows how versatile Tannoys can be. Let us know if you get them.
Good luck,
Dan