Someone please correct me if I'm wrong here...

Seems to me that all video cards display OpenGL accelerated textures in powers of two. That is, 2,4,8,16,32,64,128,256,1024,2048,4096, up to 8192.
If image files are anything in between those resolutions, the video card has to internally resize the image to display it. Assuming I'm right, that is.
So, your GPU is not only calculating the rotating and moving and zooming in/out on your model, it also has to spend some processing time to resize those images.
Is this not right? I was always told that for textures, to stick to powers of two, for this reason.
If this is right, why are the vast majority of Poser commercial textures 1000x1000, 3000x3000, or any other number of off-sizes?

Is the internal resizing negligible to GPU processing power? Does it do it only once for each image file and then keep it that way, or have to do it every time a model or camera is moved? Will it resize to whatever the next closest power of 2 size is, either up or down, or does it always go down or up?