I play regularly with Qarl's Textures Pack 3 installed.
*Looks at rig*
And my system ain't special at all.
Well, I did un-install most of the outdoor-based textures from the modification, so it ain't QTP 3 at 100%. But I do run all of the indoor textures without a single slowdown, including Caves, Dungeons and locations like that, Sewers, Prisons and so forth. I kept the rocks textures, the Aylied Ruins textures and some other textures for outdoors that wouldn't be on-screen all the time. But the bottom line is that no one forces a person to run the mod with everything it offers, and in such a case the game will still look a thousand times better than the vanilla version.