The sampling rate should be 44.1 kHz but you can play with the bit rate. The higher the bit rate, the larger the file and the longer the download.
Ogg files have average bit rates which means that the actual rate varies across the song depending on source content. The max average bit rate you can give an ogg file is 350 Kbps but I haven't found any files in MOUL which use more than 192 Kbps. And that is for music. Other sounds use 128 Kbps or lower.
Personally I don't hear any quality reduction when I compress my music to 128 Kbps, but your own ears are always the best judge.