Amp Fried?

I recently had a system installed in my car at best buy, and have had no problems for about a week. This system was in my old car for about two years, and I recently had it put into a new car that I bought. I have an older kenwood 920 max, 460 rms @ 4 ohms bridged. (it is a stable bridged amp), and 2 dual voice coil 4 ohm alpine type-Rs that are hooked up correctly. Anyways, I was driving home today, and the bass suddenly seemed to change. The subs are both hitting, but they seem to be hitting less, and the bass seems sloppy. I'd say it sounds at about half power...But only the subs sound different. Is it possible my amp fried? Or is it a bad ground? Also, I noticed that they hooked wired one sub on the back of the box to the other sub, then to the amp, whereas before I had them both running straight to the amp. Could this be the issue?  

I would suspect a bad ground before thinking the amp is fried. Fried is fried. Before an amp dies it will usually blow a fuse or start clipping pretty severly. I would run some tests on your power supply and all your points of contact. You may even find you have dirty battery posts. Good luck.  

I would say check a ground wire first. If that don`t work try hooking it up both subs to the amp seperate an see