Apple quietly updated their entire iMac lineup yesterday and they are pretty much the only game in town currently shipping the new desktop computers. This spells trouble for savvy buyers looking for a deal. It will take a week or so for authorized resellers (Best Buy, Newegg, B&H, etc) to stock each iMac model and only then will we start to see any sort of appreciable discount. It should be noted that MacMall is currently showing a $5 discount across the board but they are not specifying ship times. Amazon is also offering preorders.
Authorized resellers typically offer the best deals thanks to potential tax savings (at the time of purchase) and a higher propensity to offer discounts as way to be competitive. We saw $50 discounts only a month after the new Haswell MacBook Airs were released, so it shouldn’t be too long until the new iMacs see a price drop.
If you simply hold of purchasing a new iMac it is best to go directly through Apple and use any discounts that may apply to you (education, military, corporate, etc). If you are planning to add AppleCare to your new iMac be sure to grab it from an authorized reseller as their prices typically trump Apple direct.