Why are you considering a DC4? The Summa DC4 and Roland VP-540 are not used for the same range of signage.
Is this the same person from the other day asking about a DC4 and Roland? Odd that these same questions are coming up multiple times in less than a week.
You should be considering an Epson GS6000 and a Summa or Graphtec 64" cutter instead.
The only thing out of the list that the Summa has an advantage over the inkjet (roland) is Labels and Decals. However a Gerber Edge FX or an older model would be better and cheaper or even a DC4sx which is Summa's 30" model.
Posters should be printed on a photo printer or a printing press. Or at a minimum a 6 color solvent printer and neither the DC4 or VP540 is the appropriate machine for that job either.