Hi Beachbum

I would also recommend the software route, however the software you choose must be designed for Live Play (Sonar & Cubase are good for production but are not ideal for spontaneity, hence you pulling your hair out)
My recommendation if you wish to include everything in the software would be Albeton Live http://www.ableton.com/live-8 which is designed for your type of work. (You can also download a free trial to see how you get on)

Another option is to use your computer as a Host to control sound selection, (Including the internal sounds of your 910) so it effectively becomes a Midi Expander/controller.
NOTE: Yamaha Arrangers are brilliant as a module. (Pretty much everything can be accessed)
My recommendation here would be Kore 2 http://www.native-instruments.com/#/en/products/producer/kore-2/?src=navi for the following reasons.

1. Sound selection (Including the internal sounds of the 910) is similar to most arranger keyboards
2. It has Performance Pre-sets (Just like the Total Pre-sets on the 910) which you can set up as you would on the 910.
3. It has over 500 sounds (5GB) of its own, and has many option sound packs available
4. It will host 3rd party VSTi, with sound selection being the same as if they were part of Kore 2
5. It is very resource efficient, as it is designed for live play
6. It comes with its own hardware controller, with mappings for most popular VSTi
7. A software trial is available so that you can see how you get on with it
NOTE: You will need your 910 Midi Manual to identify channels and voice bank and program changes (These can be stored and named in Kore 2 as you use them, thus they become part of Kore 2)

Additionally if you can find a used Wersi Abacus/Ikarus with (Or add) the OAA, you can play all Yamaha styles up to T2 without converting, and if you don’t like the sounds Wersi have programed for the styles you can use the sounds of the 910 via Midi, this is because all the Yamaha style controls are available in the OAA, and because the styles are not converted the outputs will be a 100% match for the Yamaha mapping, including Megavoices
NOTE: The Wersi can also load and play Akai samples and host VSTi, so without any additional components (Just Midi and sound connections to the 910) you have instant access to a wealth of sounds.

Hope this helps

Bill