I am using Spirit of Half Life - which allows you to play scripted sentences through the player's "HEV" channel - which I initially used for VOX sentences. After realising some players might strangely turn down the HEV volume, I just opted for making sound files of individual VOX lines.
I use Audacity, which is really easy to drag and drop the files in sequence and output an 8bit wav file, it is really quick and easy to do!