Attitude AU1050 10" Stamp Frame Woofer: 250 watts RMS/350 watts max; Impedance: 6 ohms per coil; Frequency response: 25-200 Hz; Magnet weight: 50 oz.; Fs: 29 Hz; SPL: 89 dB 1W/1m; Vas: 3.50 cu.ft.; Qms: 8.20; Qes: .45; Qts: .43; Xmax: 9.9mm; Net weight: 9 lbs.; Dimensions: A: 10-1/16", B: 9-1/8", C: 5-1/16", D: 5-1/4", E: 1-1/4"

If your application is music, I would rid myself of your existing subwoofer chattel and build a pair of Critical Q subwoofers. http://www.customanalogue.com/sub_index.htm

put in a single ported enclosure. You would have to model the enclosure based on the driver parameters.  I wouldn't try to add the Polk driver to the mix. However, you would likely get better results by using two subwoofer enclosures, each with one driver, as you could then place them in the room accordingly to minimize peaks and nulls.

http://www.ajdesigner.com/speaker/bcv.php

http://www.bcae1.com/spboxad2.htm

If it's at all possible, I would recommend using 2 subs in seperate enclosures upfront: the ult atts. You can then put a 3rd one behind your chair and turn the level on this 3rd one up just enough to feel it. I have an extra sub that I do this with. It adds to the realism.

they are different.  Without published parameters you might have to measure them off the driver.

http://www.diysubwoofers.org/measure.htm