May I ask why you need an SSD for the external storage? If you're just storing random files and media, a hard drive would be much more cost effective and give you a lot more storage capacity.
Most of the benefits of an SSD are realized when you put the OS and programs on it, not so much your media files unless you are dealing with a ton of raw photos or videos. Of course, in that case you'd need a LOT more storage so even then you'd probably just want a good hard drive.
Another thing to consider is that with an external hard drive you can easily set up a partition for a time machine backup to have a bit of data security in case anything happens.