Thank you for the comments, Luc and welcome to Donationcoder! Take a look at the plug-ins for Photofiltre at
http://www.photofilt.../plugins.php?lang=en. There are a couple of white balance tools listed (though I haven't tried them). You're right about Photofiltre not being directly comparable to PaintShop Pro and the like, but as far as I can tell, there are an awful lot of people using it, or even Paintshop, for basic editing tasks, so Photofiltre is a cost effective and less bloated alternative for users like them.
As for PaintShop Pro, I took a leap of faith and downloaded the trial for X2 and wound up paying for an upgrade. I am pleased to be able to report that it is MUCH quicker and less resource hungry than either X or XI were.