Bryan,

Your amplifier may very well be able to drive the Algonquins. I'd try it before I spend money on another amp.

And 20W is probably enough. At 6 feet away, two of them would deliver 88dB at one watt. With 20W, you can get up to 101 dB or so. This should be plenty loud unless you live right next to Deerfoot (or right by Glenmore and Elbow ). If you live out in the country and don't need to worry about neighbors, by all means get another amp so you can crank it.