Bill
Greetings! Quick answers to your questions: many AVR will not be stable into 4 ohm speakers. Unless an AVR specifically says it is, that AVR is not stable into 4 ohms. In terms of receivers that likely are stable, look to Anthem, NAD as previously mentioned, Pioneer, or Cambridge audio. Be prepared to target $1,200-$2,000 reatail. Also see if you can pickup the last issue of Home Theater magazine (They have the August issue dedicated to AVRs).
Each of those brands have great raw power and should give you what you are looking for. All will have an AUX for an iPod dock or direct USB integration.
I think you willbe very satisfied with any of those choices. They are great brands that build solid equipment with an emphasis on audio quality.