606 SE should be better than 606, as
@arunkvivek pointed out the difference in specs.. It could also be expensive.. Not sure by how much.. But, if you can afford the difference get the 606 SE, else settle for 606..
A subs duty is to reproduce the low freq in music and LFE in movies.. So, you can add any brand of sub with any speaker..
The Taga TSw 120, a 10inch sub retails for approx 18K.. You can get 2 of them.. If you can get hold of Taga TSW 200, a 12 inch sub for lil more price, even better..
Choice is yours depending on how flexible is your budget.. If you are picking all Taga, good chances you can negotiate hard for prices..