rockford power 551s

Hey guys. I just purchased this amp from ebay for $150 including shipping. It's a rockford power series 551s. here are some quick specs:

• 140 watts RMS x 2 at 4 ohms
• 275 watts RMS x 2 at 2 ohms
• 550 watts RMS x 1 bridged output at 4 ohms
• stereo or bridged mono output
• 4-ohm stable in bridged mode

My questions are:

1. Was this a good deal? I thought that $150 for a power series was a steal.
2. Should I use this thing for subs or interior speakers or both? I have rockford power 5.25" in the doors with 60 watts RMS\120 peak and I have pioneer 6x9 4-ways in the rear deck that handle something like 60RMS/260peak. I have 2 shhhty 12"s, so I want to start fresh with some new subs. Any suggestions?

As far as subs I'm trying to stick with some crap best buy sells because i have a friend there who will get me stuff, and they just got an accomadation package on rockford, so maybe some P3's?? Anyway,   don't be afraid to get technical with an answer, I might sound like I don't know anything, but I am pretty knowledgable in car audio. -Dan

I had a rockford power 451s pushing a polk momo 12 and it only lasted about a year in a car I drove only on the weekends.  I hope you don't have the same problems