Two-way crossover calculator for free use. All you need is to set the impedance of tweeter and woofer, the desired crossover frequency, and the type of crossover.
The best SS headphone amp I have heard is C.E.C HD 53N.
The best tube amp is Trafomatic Audio Experience Head One.
I also like the headphone output of the great Antelope Audio Zodiac Gold DAC.
Perfect rooms are very rare. Almost every room has several room modes. According to our practice (we are local XTZ reseller in Hungary), it is very important to set the test sound level high enough, and avoid any other noise which can harm the measurement.