Software for Room Correction?

I am told that with only a microphone and $500 in Room correction? software

a person can make major SQ improvements.

Truth be told I experienced this effect recently

with a pair of Buchard S400 Mk2s at someone's home.

They went from Okay to Jaw dropping.

Maybe my jaw dropped because I knew how they

sounded in two other rooms and was shocked by the

improvement.

So who uses this gear and what do I buy???

Thanks!