Is there a difference between the two in any way other than the 6 ohm needing more current? I'm looking at a pair of 6 ohm speakers but am worried that whichever amp i buy won't be able to run them. (I don't have an amp yet) So does it make that much of a difference? I mean sure 4 ohm vs 8 ohm is a lot, but 6 ohm??? Thanks!