Another alternative, of course, would be to towerize the A1200 and use an Elbox Mediator, with a compatable PCI video card (VooDoo3/4/5, etc)... This, however, would only alow use of "retargetable graphics" (RTG) compatable software/games. It's also a bit pricey, but allows the use of other PCI devices which are ALOT cheaper than ones made for Amigas.
I would definately go for a scandoubler regardless, simply because it's the most native solution to the VGA problem.
Combine both and use a dual input monitor or a KVM/video switch! All possible screen modes in one monitor!