Pausing should help. Then Xolox is noy spending time trying to download them. However, if you really have alot of songs waiting to download, you have to think of the space in memory each of those takes up. (there is alot of information stored besides the name of the file)

I had no idea you really had near 1000 songs waiting. (assumed it was more like 20, I have noticed poeple tend to exaggerate those things) The number you can have at the same time is really best determined by exparementing with it. (everyone's computer is different)