I have cut back quite a few of the forums that I post on, even as a senior tech member on some due to the nature of the beast. It's summer, it's hot and there are stereos to install, rides to pimp and chicks to slay.
I agree with these cats, and you'll hear it over and over, kindof like car audio rules of thumb: It's all in the install (proper enclosure size, tuning, placement, power, etc.), In general, overpowering doesn't kill speakers, rather people try to get their stuff louder, turn up the gain clipping the signal (dirty power) and blow them that way (given too much clean power can also blow them, just much less common). Two good twelves with 1000W in a correct enclosure will probably out-bump almost any system you've heard. Granted 4 good twelves have the capability to outbump 2 of them, but power and install are key. If I were you and was deciding strictly between those 2 options, I'd say go with the 2 twelves. I may have the perfect solution for you though, I'm selling my 3 12's from my Grand Cherokee, and I could make it a package deal with the current amp that I'm running Directed 1100D, (1100W very clean, solid watts) and I could stay within your budget. My setup is the loudest and cleanest I've ever heard, and the subs I have compare with the infinity perfects and the JL W6's that someone else suggested. Everything is matched with everything (subs, enclosure, power). http://www.sounddomain.com/ride/410038 Check it out and hit me up to let me know what you think. If you're interested, when you send me an email we can talk about a price with the amp together. jibberjive@aol.com
Dig ding ding gain, or input sensitivity to some companys isn't a power control. It controls at what point on the volume scale the amp reaches full power. Doesn't limit the power. You also need to factor in enclosure type and size, as they both have a drastic affect on power handling of the sub(s) as well