Apologies for resurrecting an old thread.
You'd be surprised at how much faster an SSD can make a system. My first laptop has an AMD Turion X2 with 4GB of RAM; it's a Vista-era system that obviously hasn't aged well. With an SSD, it can run Windows 10 without issue. It's not able to do much beyond office-level work these days, but it goes to show just how much life an SSD can pump into a system.
CrystalDiskInfo can tell you your hard drive health. Given the E550 (I'm actually this on the same model lol) is about 5 years old, there's a possibility yours is starting to slow down, as the standard drive life is 5-7 years.
If you get an SSD and a SATA-to-USB adapter, you can use a drive utility (such as
EaseUs Todo Backup Free) to clone your current drive to the new one, sidestepping the need to reinstall anything or transfer your files.
I've got an SSD in my E550, and believe me, it's worth it. If anything, that should be your first upgrade to speed up the system.