you really don't need a amp that auto-mixes-- you can use y-adapter cables to perform the same duty(radioshack usually sells them for $2-4 ea-- you would need 2). usually there isn't much of a difference in price in models that have it and ones that don't, but just in case you locate one that has it, but is more expensive, you'll know you don't 'need' to spend the extra couple bucks..

otherwise, correct on the other stuff.