ya, it would hit A LOT harder, but before you put that on, compare the peak rms ratings of each of them, if the amp is more than the two subs added together, dont use it
Is the RMS power rating of the subs 1400w? Go by what the RMS power is; peak ratings are not true sustainable levels. The more power you have; the loader the subs will hit. Also, make sure your sub enclosure is adequate; this greatly affects the sound quality.