I've owned the Def Tech BP7000, BP7001, BP10B, SM450, & CLR3000 speakers.
I've never heard the Mythos One, though.
I no longer own any Def Techs, but I can honestly say that they sounded great.
I've also auditioned the B&W 800D, 802D, and 803D.
I thought the BP7000 had clearer midrange and 300% better bass than any of those B&Ws.
So my opinion is that the Def Tech Mythos One speakers will sound great, especially when you mate them with a subwoofer.