Wattage means nothing. Power delivered is everything. A 1000w subwoofer on a 10w amplifier will be no louder than a 50w subwoofer on a 10w amplifier. As it stands, the z623 are powered speakers, they contain their own amplifiers built in, so Yes, in this case a 130w sub will be louder than a 24w sub at the same volume settings.
As to it being worth it, that's personal. I personally have my pc hooked up to an Onkyo 100w per channel tuner/amp pushing 2x DCM KX-12 towers, 15" JBL sub and Panasonic surrounds. Loud is not the word, I cannot turn the dial past 50 or the windows get funky and the neighbors get aggravated. So will it get louder? Sure. Loud enough to suit you? Can't say. You'd have to go to a stereo store and listen to a set, or something with similar stats.
There's 3 different ways companies claim wattage. There's Peak to Peak, Peak and RMS. You can have a company claim 1000w. Sure, no worries, except it's a cheap way of making it sound big. That 1000w is a P2P value (both sides of a sine wave, the negative side doesn't count) which in reality is 500w Peak or @ 350w RMS. Good companies will use RMS values and will tell you as such.