Yes buying an A1200 would be nice. However I would never change the A500+ I have. This is the system I used to play with when I still was in primary and therefore I am more interested in upgrading it as much as possible rather then replace it.
This is about the ultimate you can do - except if you find a Cyberstorm PPC developer board which could be added into the Blizzard2060 accelerator (not been done afaik)
http://www.amiga.org/gallery/index.php?n=1801 (pics 1800-1807). Insane and hard to find parts.