The concept of bass management is to route the bass frequencies to the speaker(s) that are capable of producing bass. It's what AV receivers (and pre/pros) are doing when you specify that you have a sub connected and the main speakers are "small." Saying the main speakers are small will insert a high pass filter in front of the main speakers effectively blocking the bass frequencies from reaching them. Saying that a sub is connected will cause the bass frequencies in the front channels to be routed to the sub.
Bass management is very important for small main speakers like yours. According to the Gallo web site, your speakers have a frequency response down to 120 Hz. With speakers this small, the subwoofer will operate in a region where it could be localized. Ideally, you shouldn't be able to hear the subwoofer; only once turned off should you realize that it was playing before.
Two channel bass management built into preamps or integrated amps is very rare. A few two-channel receivers provide it. There are 2-channel bass management controllers available -- one is the NHT X2 filter. But, to utilize it with an integrated amp, the amp has to provide both preamp out jacks and amp in jacks; basically you need to be able to treat the integrated as separates in one box.
Also, there are some subwoofers that provide 2-channel bass management built into their plate amps.
Hope this helps.