Yeah, you can get a ZX2500.1 for ~600, or a Hifonics BXi2607D for ~400.
The Kicker is a more solid amp, but the Hifonics is cheaper, but still a nice amp.
You'll have to decide on an amp before you get the subs, though, because the Kicker makes its maximum power at 2 ohms and the Hifonics makes it at 1 ohm. So, if you get the Kicker amp, you'll need 2 dual 2 ohm subs. With the Hifonics, you'll need 2 dual 4 ohm subs.