Room correction DSP or using the internal EQ won't do as much as placement will for bass (and all speakers). If you're well versed using REW you will need to place your subs in various spots then measure to find the best spot(s). Once you place them in the best spots you can, then using DSP (think a MiniDSP for example) will help a little more by making frequency adjustments and also phase adjustments. Adjusting the volume levels will be up to your taste.
Best subwoffer crossover with room correction
I have a Rogue Stereo 100 Dark amplifier and Vandersteen 2ce Mkiii speakers (-3db at 29 Hz). I use an Icon LA 4 preamplifier. I have an 1. An SVS 300 subwoofer, 2. A Triad q3 inch, 700 wat subwoifer, and 3. A Snell 18 inch subwoofer with 499 watts amplification. . I tried to use the REW Software and the parametric SVS 3000, but could not obtain a smooth bass frequency response. I think I need a crossover at 70% below the lower limit (20 Hz), it will not overlap with my main speakers. So I am wondering if anyone has a recommendation for a good crossover for my subwoofer. I know that the Vandersteen Sub3 is designed specifically for my purpose and may be my best option.