Hi there,
A friend of mine has a Korg R3 37-Key Synthesizer Vocoder Keyboard which he might be selling. I was wondering if something like this would work well with Cubase 5?
I don’t really care for the vocoder mic, but in terms of creating instrumental beats and synths it seems like a good option to start with (I’ve played around with it a few times but that was long ago). What do you guys think? It’s not that cheap though so if I want a keyboard that I can play with on Cubase do you think I could do better?
Or are there any other good keyboard synthesizers specifically dedicated for use with Cubase?
That should work fine. It Integration with Cubase is just basic midi communication, but that should be enough for most tasks. You can use it to control software synths in Cubase, you may also be able to control the software synths using the knobs on the R3. (not sure if those send midi).
You should also be able to control the R3 from Cubase, both parameters and playback.
There are not really many synths that have specific Cubase integration possibilities, certainly not if you consider the R3 expensive 
Newer Yamaha keyboards like my MO6 come with Studio Connections which lets you do cool stuff like total recall. (Opening a cubase project will automatically select the right presets on the keyboard etc.). I never figured out how to even set it up properly though 