Peavey speaker Sheffield 15" Series 500

[phantomboxer]

Hi guys.
What do you think of the Sheffield 15" Series 500 (8 ohm) speaker?
I bought a pair years ago go to fit them into an old Peavey 215 bass cabinet (2 units wired in parallel, total 4 ohm). I still have it in my basement but I hardly use this rig because it is just way to loud.
I have a custom made preamp and a QSC USA-900 (450 W continuous @4ohm per channel, 900w continuous @8ohm) power amp driving the Peavey 215 and another 2x12 cabinet.
I used to think these Sheffield were rated at 500 Watt each.
Do you know the exact wattage or power handling of these speakers, and the actual price they are going for?

Thanks in advance.