Part of the setup is computer hardware related, part software, and part midi hardware ('console').
1. Computer hardware and accessories such as MIDI and Audio connections, headphones, etc. There is an excellent section on the Hauptwerk website at http://www.crumhorn-labs.com/Hauptwerk-Specs.shtml which explains the hardware choices. Whilst the computer choice was straightforward for me (I use Windows and Mac regularly for work and pleasure, but Hauptwerk on Mac won hands down!), I had to make choices about MIDI/audio interface, headphones, headphone amplifier, and touch-screen monitor, as well as the cables to connect them all. (If you want speakers- which I didn't- add these to the list as well.) Plenty of online research was involved, which I enjoyed, but I'm aware others might not be quite so keen on this.
2. Software- Hauptwerk is easy to install in itsself- as well as the CD, there is an anti-piracy dongle that needs to be plugged into USB. There are two versions, Studio and Concert, the latter having more features and a bigger price tag. Installing other sample sets is not always as straightforward as it might be as there are often multiple files to install and some choices that aren't always evident- it does depend on the way the install has been authored. Some sets (such as the excellent OrganArt Media samples) require the dongle to be updated by e-mail, but this isn't difficult. Once samples are installed, they need to be set up for your computer, and if you are not blessed with lots of RAM, you will need to make choices about 'single or multiple samples', 'stereo or mono', lossless compression and other options, all of which affect the memory used (and the sound quality); after a while it becomes easier, but it can take a lot of experimentation at first to get the right balance. Then there is the mapping of real keyboards, pedalboard, expression pedals to the sample set equivalent, easy the second time! It must be said that the software developer, Martin Dyde, provides excellent, fast and patient technical support, not to mention the active and knowledgeable userbase on the Hauptwerk forum.
3. Choosing a console and connecting it.
The easy part is connecting it! Whether you choose an existing digital MIDI console, new or second-hand, a DIY console from companies such as those Douglas mentions (and he is right that all-in-one Hauptwerk solutions exist, though sadly not in this country at present), there are plenty of factors to be considered, as the MIDI implementation of every make is slightly different. The hardware does need to be setup in Hauptwerk so that it recognises the pistons, stops as well as keyboards, expression pedals, and this can be tricky- I have had to do lots of fiddling and translation of MIDI codes for stop mapping, for instance.
Many of the processes explained aren't particularly difficult and only need to be done once, but these are the differences between opting for Hauptwerk as opposed to handing over a wad of cash to Wyvern/Makin/Phoenix etc, having the organ installed and voiced, and away you go. If you treat it as a small project, and can give it a little time at the start, then I think you will find it very rewarding. I also agree with Douglas that the cost will be no more than an equivalent toaster and most likely rather less.
D.