Maxxsonics as MB Quart branded is hit and miss with me. I have to visit shops in Chicago (where Maxxsonics is) to listen to them. When i've auditioned them, what i heard, i wouldn't buy. That's just me.
If it is a Maxxsonics made set, i'd pass. If it's original MB Quart, it's worth a listen. I'm sure you could sell them for that much if you're not happy.