Ilford Warm Tone used to come on a cream colored base, which really accentuated the warmth of the image. The newer stuff seems to come on the same white base as the MGIV paper. I don't know about the other papers you tested.
As other's have mentioned it is possible to adjust the image tone with development (over expose and shorter development in a warm tone developer). But I have found that to get a really dark black and a warm toned image on Ilford paper the best results are with the Warm Tone. I just wish they would bring back the old paper base.
Also, well seasoned Ansco 130 developer tends to color the paper base a tiny bit, and gives a slightly warm tint.