Receiver options
I would cross Kenwood and JVC off your list.
That is a great price on the Yamaha RX-V2500 and it offers the best performance of the models on your list. For comparable performance from Denon, you would have to step up to the 3805 model.
Also note, the Denon or Yamaha wont have a problem with 6 ohm speakers, but most receivers have trouble with 4 ohm speakers.