There are definitely a lot of good options out there. What are you using right now for regular old FTP? The odds are actually pretty good that it already supports SFTP. A lot of file management applications do both and lump them together, even though they're completely different protocols (sftp is from the late nineties).
If it doesn't, then I don't know what OS you're using, so I'll just recommend options for the big 3. For Windows, there's WinSCP. For MacOS there's Cyberduck. Most file managers on Linux distros let you just type sftp://me@wherever in the navigation bar, meaning you get a totally seamless experience with the rest of your FS.
EDIT: or, you can use sshfs-win on Windows and have your remote filesystem show up as a regular ol' drive, just like SMB. MacOS and Linux have sshfs, and I know there are GUIs wrapping sshfs on those platforms. I personally use sshfs at home and it's great (although no GUI wrapper, I'm a weirdo who doesn't use a graphical file manager at all).