If you're an audiophile (like me), the answers are:
1. Yes, get external speakers, either self-powered or via an amplifier. It does NOT cost a lot, 2-hand gear is often perfectly adequate. I have a good setup in my small computer room. It cost me about US$25 for 2-hand Technics speakers, and I was lucky to find a discarded Aiwa amp at the recycle centre. A plain 3.5 mm to RCA audio cable from Mac > Aiwa, speaker wire to Technics, total cost US$35.
2. No, they're not loud enough nor do they handle the wide range of frequencies to be found, for example, in classical symphonic music. For speech, and lower-level music, they're fine.
Audio quality is a pretty subjective issue, so what I've opined may well be contradicted by someone else. That's fine, you do what is best for you.