INTPentropy

Cutting a massive hole near the fan with a dremel.

Yes, laptops are not that mod friendly. I have done it atleast 4 times and 3 of them were ended up with regret. 

Well it depends on the mod, when I had my Elitebook 9470M it had a fucking terrible cooling system and got zero airflow through the fan. I took a dremel to the bottom of the case and cut a hole over the entire fan, put some mesh in there, and it dropped temps by 10-15C.
 
But I do agree, adding speakers? Not happening.

Good luck with that. Just get external speakers.

Buy external speakers? The only way to replace those is to somehow find ones with the exact same wiring, exact same power requirements and exact same firmware that are somehow better. Which is to put it lightly not possible. Making your laptop thicker for better airflow is also just not a good idea. You won't like it but at this point just save up for a better laptop. Since it's a ddr3 laptop I assume it's older so plenty of used options out there that will do what you need for not a lot.

All of those things you described can be solved easily by getting a better laptop. I have been there and done a shit ton of mods to my laptops and it all made it into a shitter laptop. 

It would be better to just buy nice speakers which connect to the laptop via headphone or bluetooth