you are actually paying a lot more for the extra 120GB hdd + 17" LCD
options :
get a external 3.5" HDD in USB 2.0 Casing. Total cost ~ S$165 for 320GB, ~$70 for casing.
opt for a smaller notebook, for portability, and use an 20" LCD Monitor at home. Dell 20" ~ AUD$549.
think should be more worthwhile by getting a normal 15" notebook + ext storage + 20" LCD monitor.