you don't need the DVD, you can as well download CDs 1-3, the rest are the sources. If you don't even need KDE you'll only need the first 2 CDs.
You can as well download the packages with wget and then create a minimal install-CD. Then while installation chose the "install-medium" "premounted directory". For a minimal install CD you'll only need the files from the "kernels" and "isolinux" directory: ftp://sunsite.informatik.rwth-aachen...ackware-13.37/
, description here: ftp://sunsite.informatik.rwth-aachen...nux/README.TXT
To download the packages
for i in a ap d e f k kde l n t tcl x xap y; do mkdir $i; cd $i; wget ftp://yourmirrorhere/slackware/slackware-13.37/slackware/$i/*; cd ..; done
hope this helps