You might but you don't "definitely need an external amp." You may need more gain, not more power. If you get an external amp that is capable of producing more power but has lower gain you'll end up with less volume, not more.
If you have it all the way up and it's not clipping you need more gain or more efficient speakers.Unless you can find out what the gain of the amp is in your receiver you have no way to determine if a given amp will have more gain unless you just try it.
If you have it all the way up and it's not clipping you need more gain or more efficient speakers.Unless you can find out what the gain of the amp is in your receiver you have no way to determine if a given amp will have more gain unless you just try it.