CorelDRAW Graphics Suite X5 :: Working With Large Images

I am working with some very large images in X5, ~ 2500 mm x 1200 mm at up to 600 DPI sometimes. (And before you say it, yes, I do need this. It is a very specific application that we work on daily and I do need the ability to basically control every single pixel at that size & that resolution). I'm using WinXP 32-bit (company mandate).

When I need precisely sized objects, I am using CorelDRAW and occasionally when I need pixel perfect placement, PhotoPaint gets the call. The images may go through both before it runs through a final backend processor (some specialized software) and then going to print.

The problem is that I am running into limits when I go beyond 300 DPI (depending on the image dimensions). For example, CorelDRAW often will fail to export a TIFF correctly when I try a 450 DPI image at that size (some TIF file comes up but nothing can load it, it's corrupted). Or for even smaller images, if I enable transparent background, I also get a similar problem. Sometimes, e.g. Photo Paint, just chokes up with out of memory problem and fails to load images at all.

Thing is, we actually have Photoshop CS5 available and while there are many things I don't like about it, it actually can handle stuff of this size. So there is also a push to get Illustrator as well under the same assumption that it will work. However, Adobe stuff is way more expensive, feels more bloated and slower and (for me at least) a pain to use compared to Corel, so I'd rather not.

Would moving to 64-bit WinXP work? Or would I need to go to CorelDRAW X6? This is already a quad-core machine with 4GB of RAM.