New set-up. What am I missing?

Hello all,
This is a first post for me. I already have ordered the bulk of what I need but am not tech savvy at all and want to make sure I am not missing anything crucial.

I purchased the console/manuals etc from midiwork and are at present on their way! I own a Mac Pro with mouse/keyboard which I intend to dedicate to HW. I have a touchscreen with display port to DVI adapter cable. I bought a Thunderbolt to firewire adaptor (read that I needed it but don't know what it does!). I also own an old 3 speaker Altec Lansing BX21 (which I have read is a 2.1 channel set-up). I have plans to upgrade this in the future but will need to wait.

I don't really know what the audio interfaces/sequencers are or if I need them (sadly even after perusing the Hauptwerk manual). If I am missing a technical device, special cable, or wire please let me know. Your advise is appreciated! Thanks.

I think you will be able to run HW off of the audio card of the MacPro with Altec speakers, as long as you have an USB input to the computer to feed the signal from the MIDI Works equipment into the computer.
HOWEVER, some level of a professional audio interface is going to give you a much higher quality sound, although the Altec computer speakers may not do much to show the difference, but even so I think you would hear some improvement.
AUdio interfaces take the digital signals coming out of HW and convert them into Analog signals that will produce actual musical tones instead of the clicks and clacks of a digital signal (think of the old days of dail-up interent and the noise it mad while connecting). They will also have a USB input to recieve the signal from your MIDI Works equipment.
If you search the forum for Audio Interface, you will find much discussion about them. Your primary consideration will be how many channels of audio you eventually want to run. To run a 2.1 system where the signal goes through a sub first on its way to the two stereo speakers, you will just need a two channel interface. If you plan on going to multi-channel setup in the future, you might want to invest in something with more channels. One the big issues for us is that most of them come with microphone inputs as well as audio outputs since most are used in recording studios. There are some however without mic inputs, which should mean more of your money is being spent on higher quality DAC's (Digital to Analog Converters).
Presonus and Saffire as well as others have some very reasonably priced 2 channel interfaces you could start with. MOTU has some higher end ones with many channels and NO mic input.
I used a MOTU 2 channel to start with and quickly moved up to an EchoAudio Fire, when it start acting up I went to an RME model, somewhat more expensive but it came highly recommended here on the forum and it did make an audible difference to my ears and the EchoAudioFire was also considered a very good interface.
Hope this helps,
John

Thank you! That was very helpful. I suppose what I have at the present will work but that around the time I upgrade my speakers I should consider purchasing an audio interface as well.