mtx 7500 vs mtx 8000

Answer:  The EBP.  From Guide: Using WinISD,  "As you look at the 'New project...' dialogue box, and click through where it asks you how many drivers you're using, you'll get to a part called 'Box type'.  It has already calculated the EBP (see it shown?) and decided whether this woofer is best in sealed or vented.  Then it made the most logical conclusion of what type of alignment (Q) based on the flatness of the response."

The parameters you would look at are listed as Fs and Qes.  The calculation is Fs / Qes to find EBP.  EBP of 50ish and the rare ones below 50 are best in sealed.  High 60's and above are best in ported.  And you have that middle ground gray area in the high 50's and low 60's where you can probably use it either way without too much compromise. 

That's always the first thing I do when I help someone out with their sub building project.  I look at the parameters and do that calculation.