Your living room about the size of a typical double story house?? That's HUGE!
I'm using M3400 as my home TV speaker. Pretty nice. That's even at a lower price point. You should drop by a shop with demo unit to test them out else you'll never know whether they can satisfy you!
Btw, edifier can go real loud without "leaking". If you get what I mean. Even my M1335 can thump some bass to your heart if the volume is tuned all the way up up and up 

You don't get me... Read twice and thrice perhaps you understand my joke. M3300SF is quite a highly recommended (for gaming...) set. But you can't expect it to perform like a hometheatre. In fact, you can't compare PC Speaker with hometheatre specially designed for living rooms. The way they sound is quite different since the area is larger than to be used as PC speaker where PC Speaker actually has Sweet spot, not to say hometheatre don't have but home theatre has less obvious difference. I don't know what I'm saying you can understand or not. haha...

What kind of sound you'll feel impressive? Because M3300 and M3300SF has different kind of sound signature, some like it some not like it.

Using USB DAC will improve details, also allow your speaker to run in by playing music for some period of time if it is new.

It's like a job. When you just started working, you need some time to familiarize and to get used to what you need to do. After some time, you're already used to it, you can perform better than when you first started.

Thumbs up for superb example?    
*Shyok Sendiri*

nope.. it's both ways... both the speaker getting loose/better and your ears adapting to the sound.

and it's okay to plug them together

speakers won't die that easily XD
your body adapts to almost anything

the only thing is the harddrive shake that I'm worried only... and that won't break that easily

Conclusion: Your way of thinking is really unique. Why I never thought that the subwoofer can kill my balls. Btw, My subwoofer is just...... around 0.6 metres in front of my balls right now. Just that mine is a M1335 and I don't really feel vibration in my balls when it goes all the way loud. I think I'm safe. You don't need to worry about your monitor getting magnetic effect for sure. Edifier does a really good job shielding all their drivers, not like L_g_tech *fanboyism*. Why don't you worry about the subwoofer may break your legs' bones? Or muscles? That would be quite fun. Oh yea, if you want some massage for your leg, put your leg on your subwoofer. Subwoofer+massage 2-in-1!~~~ The boom sound, I believe is because your bass is on. Try to turn the bass all the way down to 0, when you switch on, you hear nearly nothing *at least in both of my edifier speakers behave this way* The harddisk part... I think still ok gua. The vibration won't affect that much through air I believe.

Edit: I got no intention of making fun of it but just a little sarcasm here.

If the thing concerned were correct, the people in the club are all gone 
Not to worry so much about the bass, the vibration are still way far from killing you. Only consider the loudness you're playing, it can might to hearing damage.