You know, I was reading the specs of M80s which can go down to mid-30s Hz, and I am not sure what is the lowest range my and family members' ears can really listen at. So I am gonna experiment with crossover at 60 or even 40Hz and listen. Really I was trying to justify whether a sub is needed for my case (which is 50% HT 50% music).

However, I did a lot of searchings on Hsu and SVS since they are mentioned a lot here.

I was reading with great interest on another thread about crossover F for M80s. Learning a great deal from people like you and others on all things audio and visual !