My suggestion (mine only, others' may be different):
- Get an external drive
- Get either CarbonCopyCloner or SuperDuper
- Create a bootable cloned backup of your current internal drive
After you have the new Mac, do this
- Go through the initial setup process, and
- At the appropriate time, the setup assistant will ask if you wish to transfer data from another drive
- Connect the cloned backup
- You can now transfer your existing accounts, applications, settings and data
This -should- do the job for you.
CCC is FREE to download and it's FREE to use for 30 days
SD will do a complete clone forever without registering (if you want to do incremental backups, you need to register)