Hi Steve,
These are the three programs that I have had some experience with and have found to be very good.
I currently use Reaper the most, which is great and you can try it out for free.
http://www.reaper.fm/download.phpCubase is also very intuitive and powerful.
http://www.steinberg.net/en/shop/buy_pr ... se-75.htmlAbleton Live is popular particularly for live work and has a different style of working with loops and a sequencer section.
https://www.ableton.com/en/live/new-in-9/Fruity Loops (see below)
http://www.image-line.com/flstudio/There are many, many more, which are currently available. Some even integrate with on-line collaboration among other musicians.
The Gaia USB output means that you do not require a separate interface to the computer, you can use a usb cable between the gaia and your computer and transfer audio and midi sysex. (system exclusive commands, which is the individual patch data)
Linking the Yamaha and also the Clavinova will require at least four midi cables and small midi/usb interface.
Here are two that I use.
http://www.icon-global.com/Midi+Interfa ... e+Mi5+.htmhttp://www.roland.com/products/en/UM-3EX/You can buy a cheap £5 midi from eBay or amazon
http://www.amazon.co.uk/Proxima-Direct% ... +interfacebut they don't transmit all of the sysex correctly and can confuse new users. I have one, but it is consigned to the bottom of a rarely used heap.
Using drums with Gaia will make it essential that you have some control over the bpm setting.
I would suggest for Trance that you will learn faster if you get hold of a program called Fruity Loops. You can sync that to the Gaia from the computer clock and control the arpeggiator speed.
http://www.image-line.com/flstudio/There is also a great version on android and apple tablet computers. But only the apple version can interface with external midi, at this present moment in time, as far as I am aware.
Good Luck