I have a Roland VS-880 and a Oktava condenser mic. I want to eventually setup a demo studio but I want to know what do I need to get the best sound possible.

Do I need an external compressor?
Is a reccording booth or padding necessary?
How can I get "CD Quality " sound from the VS-880.

Any suggestions will be appreciated.

i got a vs-840.
its got a compressor/effects - they work great.

you're gonna need a phantom powered mixer board if your mic isn't already battery powered.

cd quality you get when you set (new) songs to 44.1´- pretty easy stuff. cheers

There is a collection of data for Roland VS series recorders at
http://users.ids.net/~johnwn/vs_guide.zip

It has over 400 pages devoted to the VS series recorders and related home studio data. You may find it useful.