If you are planning on expanding later to subs, and amps. I would suggest a HU with Sub-level RCA Preamp outputs. This allows you to control the level of the subs with out adjusting the gain on the amp itself. It also allows you to keep the bass down on your interior speakers.
I just purchased a Pioneer P8400-MP from
Buy Digital Direct for $319.00 with shipping. These HU retail for $600.00.
You could go with a lower priced HU, but I would suggest making sure you are getting 3 sets of RCAs(front, rear, and subs).
Just My Opinion.
Joe