I'd get a Rockford amp to match the subs..
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Anyway, your subs are running 600-RMS a piece.
So, you want to at least get 600 watts x 2 channels or 1200x1
RMS amp.
A lot of amps will advertise '600' or '1200' watts, but that's their max power, not the power they give out continuously.
EDIT:: (Also, a lot of subs will say '1000 WATTS!' But that's their maximum power load... not continuous.]
So, an amp that you'd want would be:
600 RMS x 2 @ 2/8 Ohms [More realistically is 2-Ohms since 600RMS @ 8-ohms is a ridiculous amount of power. The higher the number of ohms, the more the resistance]
Or a 1200 x 1 @ 1/4 Ohms [Again, more realistically is one ohm.]
You can get a cheapo amp, but who knows how long that'll last you? You know? I bought a Boss amp (which aren't the best amps-- but they're pretty cheap) and it's lasted me probably a little over a year, and still running strong.
But you can also spend like a ridiculous amount of money to get a pretty, effecient and pretty amp.
So no one can really tell you unless you give us a price range.
EDIT:: Also, there's always great deals going on in the Classified section. You can find some great deals on some great subs. I just bought a 1000 watt x 1 channel for $105 shipped. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif