OneWorld,
The best thing to do is to get the iMac and see if
NeoOffice does what you need it to, Office-wise. It's free, so you've nothing to lose. It is "aquafied", Aqua being the current look of the Mac OS. It's a more elegant solution to the "raw" porting of OpenOffice which requires you to use X11.
If you don't need a spreadsheet, you could consider
Apple's iWork, easier to use than Word and PowerPoint with powerful templates and effects. You can also export the files to Word and Powerpoint.
Rather than use Boot Camp to run your Windows applications, you could get an emulator, such as
Parallels and run office in it. The Office applications aren't graphically intensive, so work fine in emulation. This way, you have access to the virus-free Mac OS at the same time.
AppleMacster