DPI ability, from the standpoint of 3D rendering is, I think, a bit irrelevant.  I generally create an image with a specific POV and detail.  I then consider what size I want the printed scene to be -- based on that initial creative concern of POV and detail.

I target a final DPI of about 240 for final print resolution, and based on the size of print I want, I simply do the math (8x10 print would require a final image resolution of 1920x2400 pixels).  I use Irfanview to do a 2x upsample (usually with B-Spline or Lanczos filters), so I factor that in if the rendered file will exceed ~2600x5000 pixels (in other words, don't bother with pushing the limits, just upsample).  I have PShop CS2, but IrfanView does a better job at upsampling.
I print to my Epson 9800 giclee printer, usually on canvas (which I then coat with a giclee veneer).

BTW, if you ever want to buy a wide format giclee printer, and want to print on canvas, then seriously consider the Epson 9800 or 7800 printers.  They are made on the Seiko assembly line, and are absolute jewels!