Nick_si is correct about "special" dealer models. Costco and other retailers do this as well. One of the reasons it's done is so that the consumer can't price match for a better deal because you're not comparing the same model (2500s vs the 2500 in the above example). Denon, Onkyo, and Yamaha all make good systems so I'd pick a price point that you're comfortable with and then come back for suggestions.
I just looked at your links so it appears that around $300 is your price point?