Depending on the amp, very true. Amps work harder running at a lower Ohm levels, therefore operate under a lil more harsh conditions, therefore will not preform at optimum potential under stressfull circumstances. This difference will simply depend on the arcitecture of the amps cicuitry, components within, and the qualitly of the drivers in your high end and subs. But Better amps will hold tighter tolereances throughout operation than cheaper ones, thus creating a better consitant output. The only major sound difference you will hear goin from 4 to 2 ohm, is in the output dB level increase due to the power output that increased by the factor of the ohm load. Hope that helps a lil . .. ..
And Nate, for what else it's even worth, I can tell an audible difference from the same setup, 4 ohm versus 2ohm, but its kinda hard to measure whether it actually has a less distorted output, or its just the actuall dB increase. To me, things sound cleaner at 4 ohms than at 2. But sound punchier and slightly more forced at 2 ohms. I mean if you think about it, just merely droppin the load from 4 to 2 puts you equipment in a higher bracket of operation, which simply can be translated into "it just sounds better at lower power handling". In the grand scheme of the electrical world, current should be more stable at at higher ohm loads than lower, just 2 more cents.