for typing you want either cherry mx blue or browns.
browns do not have the audible click sound so will be quieter.
on top of that you can add rubber o ring dampers under them to quiet it even more.
bottom video for sounds.
http://www.wasdkeyboards.com/videos
as far as what to buy... perhaps this ducky zero... and then buy some o-ring dampers from wasdkeyboards or another source
http://www.amazon.com/Ducky-Zero-Keyboard-Brown-Cherry/...
normally they go for about $80 (at least on mechanicalkeyboards.com they do)
another option might be the durandal (again you can buy some o rings for it)
http://www.maxkeyboard.com/max-keyboard-durandal-g1n-me...
about the same price as the ducky.