personally, i would remap the eyes and any other parts you want a high resolution for so that it takes up the whole uv space, and then use a smaller map. a 700 x 700 texture map in which the eyes take up the whole map is gonna be better than a 3000 x 3000 map in which the eyes are still only taking up 500 x 500 pixels of space on. I usually map my figures into 5 seperate templates, one for the body, one for the face, one for all the other head textures, one for the eyes, and one for everything you want to make transparent (eyelashes, eyebrows, pubic hair, eyeball) That way you can have 5 1000 x 1000 texture maps that still have a higher resolution for most materials than the 3000 x 3000 and 5000 x 5000 hi res maps. Of course, a large amount of ram will still help.