And by my calculations the cartidge heaters are good for ~ 40W at 12VDC (if both used) and ~95W at 18V if both used. 24V a single heater is over 80V. I am looking at this power supply:
http://cgi.ebay.com/ws/eBayISAPI.dll...category=32720
or similar. Something that'll go 12-18V would be ideal, but even at 12V (and under 4A total) the die sim should work ok.