re subs, us amps

I am trying to hook up 2 - 12" RE SR subs to 1 - US Amps MD1D. These amps have 2 separate speaker outputs. The speakers are 4ohm DVC. How should I wire these? Series or Parallel? This is only used when there is one speaker output on the amp, right?

It's a mono amplifier. The two sets of terminals are for ease of installation for multiple woofers, AND INTERNALLY PARALLELED! This means that if you connect one 4 ohm load to one set, and a second 4 ohm load to the second set, the amplifier sees a 2 ohm load. With those speakers, you can get a 1 ohm load (each driver in parallel, one driver connected to each terminal) a 4 ohm load (each driver in series, one driver connected to each terminal) or a 16 ohm load (all voice coils in series, both drivers connected to one terminal)It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Which would be the best in your opinion? I would rather have it with better SQ than SPL.

Is the amp 1ohm stable?  If so you can do the following.  If it is only 2 ohm stable, do not attempt.

If you parallel the coils on each woofer, and connect each woofer to the relay setup below, you can have the best of both worlds.  The amp will be running either 1 ohm or 4 ohms, depending on the state of the relays.

When the relays are at rest (normally closed position) the woofer coils are wired in series. When ground is applied to each coil (energizing the relay coils), the voice coils are wired in parallel. With 2 four ohm voice coils you'll have an 8 ohm load at rest and a 2 ohm load when the relay coils are energized.

For each dual voice coil woofer that you want to change from series to parallel, you'll need two relays for each. They can all be controlled from the same switch. 

If you wire those subs at 1ohm be careful with the volume knob. That amp is rated at 1200 watts rms at 1ohm. Your subs are only rated at 300watts rms each. I have push those subs with 500watts a piece with no problem but be careful.ieSpell rocks.