^^ Are they all original and specific to the US/C region? Or are you going to use the Swap Trick method to play em?
If they are all original's then you have no worries, trust me, i had to search for quite a while till i got a hold of the 60GB and this was quite some time back. I wanted to get the 60GB coz i get more for the price that i pay, but if you already own a PS2, then 40GB is the way to go. And 80GB is not discontinued (i havent heard of this).
Good Luck!