Try doing a file copy task from win pe to copy the ghost files to the local c drive. I don't that this isn't a image deployment but would give you a feel for how fast can X ammount of data make it from the server to the client while in PE.
Map a drive to the server say. I: and then while in the folder for the ghost image do a copy *.* c:\
Would help with getting you the minimum time to shoot for. Also might try with a higher compression on the image so that it will be smaller yet. The cpu on these new systems shouldn't be the slow point any more so higher compression other than a higher opportunity for corruption should not be holding back performance the way it used to on slow cpus
Also is your PE and server NIC driver the most recent? And is your PE connection set at 100m or 1g? I know the desire would be gig but what does the switch indicate is it actually connecting at gig speeds while in PE. In the DOS days you could configure the driver to connect at differnt speeds I am sure PE is the same but I hadn't actually looked for it.
Is the speed measured at the client or at the ghost cast server? Not that it matters to me but keep your measurement consistant because the ghost cast server will be data sent across the wire and the client will report data written to the drive so the two speeds don't match up. so as long as you keep your measures ment in the same place you will be good.
As for speeds my stuff is virtualized now and that takes a hit on performance so I know I am not as fast as I could be.
Hope those are some helpful thoughts. Especially the copy test I like that one to see what the best case times are.