The room is around 30sqm... I'm using the old PSB Subsonic5 (10in) and it's not enough...

It would definitely be cheaper if i were to purchase the new Subsonic5(10in) and have it paired with the old one.... Would having both subs sound better,stronger and deeper compared to just one 12 inch, the more expensive B&W ASW650??

The Onkyo TX-SR602 is my receiver... tnx