Adobe offers trials of InDesign Server, though I think you have to email them to get it started, it's not just a public web download.
I wasn't aware there were performance optimizations in InDesign Server. I would imagine it'd be approximately the same speed as InDesign Desktop if you don't show the window where the work happens.
Yes. There are performance advantages to Server -- mostly because none of the UI related processing is necessary...
Don't expect the differences to be too drastic though. I have found that the 64 bit Windows build to be noticeably faster than my local machine...
(P.S. If you do decide to go for a Server license, I might be able to get a discount for you...)
Thanks for the replies. I will look into getting a demo version as soon as I can.
Thanks also for the offer Harbs, I'll let you know!