Like one of your images, clip the backgrounds out on the several black-background images and use a colored rectangle behind them for the black.

Unfortunately, even if you remove the backgrounds from those images, if they sit on a 100%k rectangle, they will "merge" with the rectangle and the result will be some areas remaining the rich black (K plus the CMY color components).

An alternative to clipping out the backgrounds is to change all but the text to a rich black.

Another alternative is to remove the black in an image editor and use another application to layout the ad. PagePlus works for this using these images with a transparent background on a 100%k rectangle.