sounds like a good starter system.
I'm betting you meant a Pioneer DEH 5000 instead of a Panasonic...

(that's okay, Pioneer is better than Panasonic anyday.)
The Rockford is a good amp. Better than most of the crap you can buy now- especially the Rockford they sell at Best Buy now... It's crap compared to the older stuff..
Depending on what impedance your subs are, I'd suggest looking at bridging the subs on two of the amp's channels, then run the front speakers off the other two amp channels. Let the rears run off the head unit.
If not, run the amp in 200x2 like you mentioned and just turn the gain down so you can hear the rest of the speakers...
THEN when you're ready to upgrade, buy a larger 2 channel amp and run the subs off it and keep the rockford for your main speakers.