Running a car audio amp in parallel mode, is it okay?

I have a 4 channel car amp, and I plan to use it to run two 10" subs. People generally use two channels per sub in a bridge configuration. I do not want to do this, because by wiring the two amplifier channels in series, it doubles the output impedance of the amp. It also halves the output load on the amps from 4 ohms to 2 ohms, for a standard 4 ohm sub.

The reason this is a problem is that it reduces the damping factor of the amp/speaker by four times. The damping factor is the ability for an amplifier to control the movement of the cone and reducing any unwanted movement. The higher the impedance of the speaker and the lower the output impedance of the amp, the better this figure will be. Only problem as that with a higher impedance load, the available power output goes down. Damping factor is simply the load impedance (speaker & connecting cables) divided by the output impedance of the amp, or its self impedance, generally anywhere between 0.1 and 0.01 ohms.

What I actually want to do is wire the two channels of the amp in parallel, thereby halving the output impedance of the amp, and doubling the damping factor, and also the amp will be able to handle a load impedance that is half of what it is normally. Is it safe to wire the +ve terminals together and the -ve terminals together? To my knowledge most amps now are floating ground and one half of the amp has a reverse phase input and corresponding output, to make bridging easier. Are there any amps that I can wire the two channels in parallel?