Honestly, it's technically better for car audio to run the amp at 4 ohms if you're after sound quality. The problem is that most amps put out considerably more power at two ohms, so to get a lot of power from an amp, you either need to run at lower loads, or buy a relatively expensive, large amplifier to get the samw power at higher loads.
The system won't sound "bad" at 2 ohms.. but on paper, or on a scope, you'll get better headroom and SNR with lower distortion and superior damping by running at 4 ohms instead of 2. If you'll actually hear the difference may be a different matter entirely.