Digital BW, The Print

Hello,
I've recently recieved my VM Quadtones. I'm printing with a 1280 and 
for the time being using EEM. 

I went to MIS's "workflow" page and got the curves and read through 
the process. I first tried to print an image I've been working on. I 
found most of the shadows as well as any light to dark transitions 
were posterized. So I figured I would go back and start with the 100 
step wedge. I couldn't get a decent looking wedge, I kept getting 
flat spots usually between 60-80 and a little more around 45. So I 
decided to change some things around. 

Instead of converting to sRGB I went to AdobeRGB('89). I was almost 
there, so I changed the paper type in the driver to Matte-
Heavyweight. Now it's looking very nice. I tried printing with the 
transfer function a couple times. I noticed flat spots around 25, 45 
and 65 both times. 

Tomorrow I will start trying images out to see if these settings 
still hold true. I also got sample packages of Legion, Arches and 
Hahnemuhle that I'm eager to try out.

A couple questions:
1. How subtle is the cool curve? All curves besides the cool give the 
intended results. I didn't think I would like the warm tones, but 
just from the wedge, the medium-warm looks very nice.

2. The process states converting to grayscale, editing, then 
converting back to RGB. My question is, what's the difference between 
converting to grayscale and back; and just leaving it in RGB the 
whole time using adjustment layers/plugins for b&w effect?

I would greatly appreciate any advice or thoughts. As I still have a 
lot to learn, though it doesn't seem as overwhelming as it did 2 days 
ago ;)
Thanks again.

matt betea