My tower speakers have side-firing 15" woofers.  They are unpowered and completely independent of the 3-way speakers in the upper half of the enclosure.  I want to use these as my two subwoofers connected to my 7.2 Yamaha TSR-7810 

My HT room is small, so I don't need gobs of power.  Seeking recommendations on the subwoofer amp setup. 

1. two separate. discrete amps each with their own power supply?
2. two separate, discrete amp boards running off of one power supply?
3. a stereo amp with right channel running one sub and left channel running another?
4. do I need volume/gain control on the amp or let the receiver's LFE settings drive the output and cutoff?
5. are ground loop isolators a prudent move for the 7.2 LFE outputs?