Quick AMP Question 4 or 2 channel?

I'm looking at amps to power new speakers for my car, I have a 4 speaker system. The headunit only puts out 2 channel stereo I believe (Sony Xplod), and there are more choices for 2 channel amps. Should I just get a 2 channel to power stereo left and right, or would it be worth it to pay more for the 4 channel? TIA.

I would go ahead and get a 4-channel amp and use a set of y-splitters for the interconnects at the amp to get the four input channels taken care of. That way if you ever upgrade your head unit, you already have an amp in place that can take advantage of a four-channel head unit.