I would get all new sand (not live, just whatever type of cheap sand you prefer) and seed the top layer with your old sand. If you can get other types from other people, that's always a bonus, anytime.
To much junk is stored (especially in the lower layers) to take all yours with you, and it's not effective to wash.
I just did this (55g to 80g) and I took about 1/3 to 1/2 of a 5 gallon bucket full (from the top layer in the 55g) and it worked for me. Most people only reccomend a few cups of established live sand from other tanks when starting a brand new tank to get a huge jump on turning all the sand live anyways. Plus I am guessing you will be moving a bunch of established live rock to, that will speed everything up as well.