As far as the EQ options currently available (Behringer, R-DES, SMS-1), it is probably the most potent single package. If you have a need for EQ, it's definitely worthy of consideration and would be my recommended tool for the job.

Unfortunately, it's impossible to assign a specific scale for amount of impact it will have in your system because I don't know how much need you might have for EQ. The first line of defense in this case should always be room treatment and speaker placement, as this yields the best results without direct manipulation of the audio signal. In a space that is acoustically friendly (due to specific acoustical treatment or just good luck), the SMS-1 will still be able to provide benefits, but they won't be as drastic as in a space with significant untreated problems for it to address. My system is in a room that's inherently pretty acoustically friendly: a good mix of hard surfaces and soft, relatively fortuitous subwoofer and speaker placement, and no really nasty peaks or dips in frequency response. For me, the SMS-1 was still able to fine tune the sound to provide a smoother integration of subwoofer and speakers and to reveal somewhat greater detail in sound in the lower octaves. The impact in this case was not huge (maybe a 3 for someone familiar with the system). If I'd had a more difficult space (such as my old living room), that impact could be far greater.