Designjet 800ps slowness

Hi, we just bought a Designjet 800ps, switching from a Designjet
488ca, and at the moment we are a bit disappointed by its speed
performance (we only print technical drawings, from Windows XP
clients).

First of all, the speed while actually printing does not seem much
faster than the old 488ca, although the quality is of course sensibly
better; you can gain much speed by printing in low quality, but then
it's lower quality than the old plotter.

But what really puzzles me is the time needed for processing print
jobs: e.g. we have a PDF file created from AutoCAD using Acrobat, it's
a bit heavy but the file size is only 4.4 MB after all; when I print
it (from Adobe Reader), the computer works for some seconds, and then
starts sending the file to the plotter (the front panel displays the
job name, and I can see the file being sent in the computer's print
queue).
I did two test prints of the same file: a first one using the HPGL2
driver and setting low quality, the job size in the queue grew up to
37 MB and it was over 15 minutes before the plotter even started
printing. In the second test I used the Postcript driver with default
settings, the job was over 60 MB and it took 30 minutes to start being
printed!

We never had such long waits with the old plotter, which by the way
was connected to the network through an old HP Jetdirect print server.
The new 800ps is of course connected to the LAN using its internal
network card.

Is it normal? Is there a way to speed up things?

Thanks.