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I think it's fair to say that if you can dream it, XOOPS can fit it.
with that in mind...HTML is very linear (left to right, top to bottom) The only way to get away from that is by using graphics/images to create the illusion of non-conforming lines but doing so will limit your ability to take advantage of some of XOOPS dynamic features. example: navigation.
Other than that, you can tell XOOPS to place the blocks whereever you want them. You can also change the blocks themselves to fit your design. It may take a little more work but it is possible.
if you provide a sample link of what you are trying to accomplish XOOPS can do it. Unless of course you want a different look and feel on every page of your site which isn't very user friendly anyway.
There are plenty of folks here in the forums that can help you create a theme(for a fee) based on your vision of a "perfect website design".
Hope this helps,
-Builderb