I go funan 2day, so far does not have W520 and T420s display set yet.
Tested out X220 and T420. X220 sound seems over-rated by review, loud enough to fill up large room, but i blast full vol, the sound seems weaker than T420.
T420 speakers sounds a bit louder than W510.
Tested out and it seems that they have fixed the EQ issues from the W510 series.
E220s and E420s have Dolby Home Theater 4, but I does not see any switch to on or off it + this 2 laptop SmartAudio does not have EQ. (Maybe they did not upgrade their drivers..)?