@X-ray:
Keep the A4000T, but start building a separate A1200T as well.
If you plan to upgrade heavily, if you ask me, it's always better to go by the A3000/A4000(D) or (T) route, as they are superior to A1200 and much less hacky, but don't get me wrong, A1200 is right up there (almost) with A3000/A4000.
If only you could find a way to solve the memory problem... :-)