Honestly I think you'd spend just as much money on electrical to run .5, then if you were to buy an amp that puts out 4k at 2ohm. You could do 2 amps, one on each sub. And strap them for a final 2ohm load.
To be honest, that AQ amp will probably put out more than the soundstream would.
just because AQ underrates their amplifiers. and you will be getting a better bang for the buck.