Digital BW, The Print

You are right, those were the output resolutions. 

For a 12x18 print, the service bureau offers: 

100 dpi (1200x1800) which is a 6 MB file;
200 dpi (2400x3600) which is a 25 MB file; and
300 dpi (3600x5400) which is a 56 mb file. 

I am wondering whether these desktop printers I mentioned (Epson Photo
2200 and 2400) can use all the information in the big files?

A.