All the above would work, but for me, I'd take the opportunity of a clean build, buy an external drive case for your current hdd
First ensure you've got all the serial nos etc for Windows and all your other programs.
Then swap the drive and do a clean install onto the SSD.
Then install all your other software on the SSD.
At that point install your old HDD into the external case, connect it up and copy over all the data you want to keep (havea spring clean), as a safety measure you might want to wait a while before the next step, just in case you've missed something you might want.
Now you can format the old drive, set it up for backups, and if you need it you've got a physical backup you can take to a different location.