And that's how I had it wired.

I just bought a brand new Type-R yesterday, that will actually be able to handle power.

BUT i still have the problem where the sub hits about half as hard after like, 10 minutes of listening to it!

Anyone have any advice on that?

 

honestly, get your amp checked. i had a kenwood that did the same thing to me. it ended up having a "dead spot" on the board internally. this means i toasted the amp. hopefully you didn't do the same but it is possible.