You can use software like X-Over pro which is rudimentary compared to LMS plus many others that will graphically show what the changes would be . In the end is comes down to measuring with a good microphone out in the middle of your yard on a quiet day using software like REW to get a desecent frequency response. Then you go inside whre your room screws with everything you ever knew about sound then back to the software change some components on the crossover, back outside when the right conditions are met run tests, rinse and repeat. OR just build the crossover as it was designed and enjoy. Both ways are perfectly acceptable.