GTO2Z28

Right now I have just ONE Infinity 10.1 with the Viper's and the 2 Hifonics amps. I am thinking about buying one of Subthumps' passenger side boxes, adding another 10.1, possibly some rear-fill, and upgrading amps. What do you all think? Here would be the setup w/o the rear fill (really do not think I need it).

Infinity Perfect 10.1's
Frequency Response: 18-150 Hz
Recommended RMS Power: 350W
Peak Power Handling: 1400W
Impedance: 4 ohms

Directed Viper 650.2's
Sensitivity: 89 dB
Frequency Response: 58-25,000 Hz
Recommended RMS Power: 125W
Peak Power Handling: 175W
Impedance: 4 ohms
http://www.sounddomain.com/sku/DEI36065

Current amps: two Hifonics Industria amps, Pegasus (100x2@4, 200x2@2, or 400x1@4 bridged--what is to the single sub right now) and Gemini (50x4@4, 100x4@2, or 200x2@4 bridged). None of the literature states if that is rms or peak, and those ratings are stamped on the amps, boxes, books etc.

Do you think I should add the additional sub? If so, what do you think i should do about amps?

Also, I am going to change out my JVC HU and 12 Disc changer for something more "modern"...maybe touchscreen, any suggestions on that? Thanks!