When I need an all white fabric I use RonLoc #404 Bleached muslin. Its a good quality and has none of the slubs , etc . I have purchased it by the bolt, so its been a bit since I needed to buy any , so not sure if they have reduced the quality.
Ron Loc has many many different grades and I think there is one of even higher quality than the #404.
As for the cream colored , I have pretty much abandoned the use of a solid , as I find the tone on tones so much more interesting in a finished quilt. But before the tone on tones became so widely available ( more than a few years ago) , I used the Ron loc muslin , High grade, but do not have the number for it.
Maybe ask for some samples to see what the current quality feels like. They also make a 120 inch wide muslin.
Ron Loc makes so many variations :
http://www.roc-lon.com/products/muslins.html#