Before I got a printer I used Lab services.
I got the Labs. printer profile and used the Labs requirement for dpi, one Lab required 300dpi another required 402dpi
I had no problems, the problems started when I got my own R1900
Some labs would not provide profiles saying they did all the necessary adjustments to get a perfect print everytime. They did not get the job.
So, I would think best to do all the final print file creation with Qimage, then at least if any thing is wrong with the final print you have only yourself to blame and have one point to correct things.
Jeff