Can I "double-wire" speakers?

I agree with Unsound. Not only is it unlikely both amplifiers would have the same gain, but they will also have different characters and this will occur at the crossover point. Speaker manufacturers make every effort to develop a seamless crossover. Why mess it up? So, if you have an Onkyo receiver and a Sophia Electric the answer is no. If you have two identical amplifiers the answer is yes.

The answer is likely no but that isnt known till you try it as far as gain goes.

...Or find out what the gain of the Onkyo and Sophia Electric is. Though there are exceptions, I think Rrog's advice is sound.

Use one amp and bi wire. I use purist maxinus bi wire for my mids and highs and bi wire purist elementa for my bass. Two sets of bi wire from Krell to B&w speakers. Basically, I have one amp and speakers quad wired. Using two amps that are not the same will create a muddy sound signature. Like speaking American English and British English at the same time. Be carefull, take you time to set up. And make sure everything is powered down.

Hi Simao,
Just because you "can", doesn't meant that you "should".
The Titus has a very high frequency crossover, and is also very easy to drive, so IMO bi-amping would be wasting most of what you can gain from the Sophia's presence to give you an incredible mid-range.

Alternately use your second set of speaker wires to set up a line-level feed to active sub with crossover of 55-60 Hz.

Or, bi-WIRING (not bi-amping!) is good to try, where you run two sets of speaker wires from the Sophia output terminals, with one set going to the high-freq posts and the second set connecting with the low-freq posts (jumpers removed).

If single-wired to speakers, try replacing the stock jumpers with connectors similar in grade to your speaker wire.

Good luck with your Sophia, and please let us know how it all comes together.