I would look into either an alpine cda-9884 or cda-9886 with an alpine pxa-h100 processor. I know that a lot of people will probably tell you to get the cda-9887 because it is a nice head unit that offers great ipod control and great processing power all in one package, but I have few reasons for choosing these head units instead.
Both the cda-9884 ($160-$200) and the cda-9886 ($220-$300) are less expensive than the cda-9887 ($290-$400). Both the cda-9884 and the cda-9886 come with ipod cables which is not included with the cda-9887. Of course, the cda-9887 has much more powerful built in processing than either the cda-9884 and the cda-9886. However with the cda-9884 and the cda-9886 you can easily upgrade if you decide that you need more processing power. A cda-9884 or cda-9886 equipped with the pxa-h100 ($150) has the exact same processing as the cda-9887. Not to mention that if you want to use imprint autotuning, all you need to do is purchase the alpine ktx-h100 ($30) tuning kit. If you wanted to use the same imprint autotuning with the cda-9887 you would have to purchase ($250) or rent ($50) the ktx-100EQ tuning kit for the cda-9887. In addition, you mentioned that you wanted USB and the cda-9886 does USB as well.