Bridged, 4 ohms: 700 watts x 1 chan.
Bridged, 2 ohms: 900 watts x 1 chan.
Now, I wouldn't recommend bridging a Class A/B amplifier to connect it to a 2ohm subwoofer. The efficiency and heat will probably be pretty bad. So, GT-2200 is optimal for using with a 4ohm subwoofer. The Soundstream REF gives you best Power a 2ohm. So you're not comparing apples to apples. If you have 2ohm subwoofer, then I'd use REF..
Personally, though if I needed >500watts at 4ohm, I'd buy a PPI P600.4 (600watts with 4ohm bridged) or PPI P1000.1 (600watts at 4ohm but you can also get more out of with with 2ohm sub). They're very efficient and tiny. The P600.4 costs only $140 online.
Of course, if you have the space to install the surfboard that a GT-2200 is, I don't see why not. It's almost overkill. It's clean enough to power reference quality speakers.
Re: soundstream ref1.500 or boston acoustics g2200
i plan on running two svc 4 ohm subs and my thoughts are the same as yours i just dont like the idea of running an a/b amp on a 2 ohm load either, but for that kinda of power, i just can't stop going back looking at the BA. But as far as the soundstream i've always wanted a blue box so it's a certain amount of CA&E nostalgia for me.