How to define SPL n SQ?

I dun really listen to rock music, but I like to listen music loudly. My stock 4" speaker, start to have crack sound after volume 40 which is just ok ok loud for me.

Ok, I listen to Jay, Kenny G, Timbaland n etc. Not really into Linkin Park or those really noisy songs.

For those songs, I like to listen them loudly.

So am I more into SPL or SQ? N which model suit me more?

I am considering Pegasus as there r too many imitation Sound Stream in the market. But I worry that it is not loud enough as it is build for SQ. N i am not sure the way I define SQ n SPL.

U mean ur fren car using PG65?