I'll offer up a couple of sugesstions to look at!
First off if you are not into spending that much you are better off powering your fronts/rears with the HU for now. That way you can focus on not going too cheap on the subs and sub amp. Save up and get a nice 4ch amp for the kappas later.
Here's my suggestion for subs and sub amp:
Go with a 400W RMS setup for starters. That's some decent bass power that can be had for under $400 with decent quality parts.
Get a mono amp. These are Class D amps that designed for running subs. They are more efficient, draw less current and produce less heat than multi channel amps. They have more distortion than multichannels but that's ok since they are driving sub bass frequencies where distortion is not easy to hear. Here are 2 decent amps that produce 400W x 1 @ 2ohms:
Kicker 04KX400.1
Kenwood KAC-8151D
For subs you are going to want to match the RMS power rating of the amp that is powering them as close as you can. I've always been a fan of Rockford Fosgate subs and here's a couple suggestions:
If you want a single 12" sub check out this one:
Rockford Fosgate RFP4212 12" DVC Sub
If you are still set on having two 10's then give these a shot and wire them in parallel for a 2ohm load:
Rockford Fosgate RFP4410 10" SVC Sub
Either of those amps with either choice of sub will get you what you are looking for for under $400 (not including the enclosure). A good deal IMHO.
Don't forget to follow the advise of MyEarsHurt on the wiring and I might also add that you'll want to install a power distribution block (such as
this one) as well so you will be set for adding power to additional amps in the future.