Hi dudelsack. I can relate to your frustration. The Web is certainly not like Print.

If you have Dreamweaver, do you have Flash? If so you can bring your Xara artwork into Flash and then when placing your Flash (SWF) file into your web page you can set the background of your flash movie to be transparent. I believe that will give you the results your looking for and save you the hassel of trying to line up a tiled background with your image. I've done this many times and it works great. If you want to see a sample here's a link to client site I developed quickly using the concept: http://lri.bigplan.net/sdbp/working/lri/index.htm
Granted, I'm not tiling a background across the whole page, but the column on the left is a background graphic and the header and navigation are Flash with the background set to be transparent overlayed on the column. No aliasing problems here.

Hope this helps.