There are a few important things to keep in mind when looking at guitar videos.
The sound you hear may not give a good representation of how the guitar really sounds. There are many variables in making a guitar video. Were room mics used and if so what were they? Could be cheap mics with the wrong frequency spread. They would then miss some of the nuances of the sound.
What software was used to record the sound and was any processing added?
When a video is uploaded to youtube it is processed and compressed. This can play havoc with the sound dynamics.
You could buy a guitar based on a video you have seen and then wonder why it does not sound the same when you play it at home. And this is why it is important to always play the guitar yourself before you buy. I know it is not always possible. Sometimes the store is too far away or they don't have the guitar you want to try in stock. In which case always buy from a store that allows returns. Just in case you don't like it.
The FSX-800 is the based on the FS800 and is a smaller bodied guitar than the CPX-700. It is essentially what is known as a Folk Guitar. If you want something closer to the CPX-700 take a look at the FGX-800. As it has a larger body and will project better.
The CPX-700 is actually a sort of mini Jumbo size guitar. Larger than an auditorium but smaller than a full jumbo. So it is larger than the FGX-800.
The reason why I suggested a smaller guitar is because it is much easier to control the dynamics. A CPX-700 sounds wonderful when strummed but it takes more effort to play quietly. You can certainly do it but it is not ideal. This is why there are all these different size of guitars. Some are suited to one purpose more than others. It is why I have more than one guitar. Well, it is my excuse for having a lot of guitars
Do you live too far from the guitar store in order to go in and try a few?