Stay away from the kenwood. If the pioneer is a model 1014 or 1015 then it is a fantastic value, very high on the bang for the buck and overall quality. Have you ever considered getting a Harman Kardon receiver off of their Ebay store? They are refurbised products but any repairs that were necessary have been completed by Harman themselves and there is a full Manf. warranty with the purchases. You could get a 235 or 330 for under $400. Both are decent. All of the receivers you are looking at seem to be fine choices except the Kenwood IMO.
Edit, names changed, thanks Bird, shouldn't write w/o coffee.