Brother HL-5170DN expansion memory - is it worth it?

We are evaluating the Brother HL-5170DN that comes standard with 32MB.
Will be printing mainly PDFs and PowerPoints from a networked workgroup of 2
to 6 people. The largest document size is about 3MB. The printer seems
like a good performer with the standard 32MB RAM -- does anyone have any
real-life experience boosting the printer by another 128MB and see any
improvement?

Does Postscript mode print PDFs better/faster than PCL?

Does anyone have any insight into any new models that Brother might have in
the pipeline? I'd hate to buy a bunch of 5170DN's and find out next month
that they have a newer/better model....

Thanks.