Not sure of your budget, but a double DIN unit such as the Pioneer AVIC D3 would go nice in there. It's a touch screen unit with navigation, DVD, XM and Sirius capability, and will control and charge your Ipod with the optional Ipod cable interface. I just installed this unit into a customer's 03 Yukon the other day. He wanted both XM and Sirius services, Ipod, and a reverse camera installed also. It's a nice unit and is very popular in my area. You can shop around and should be able to find this unit for under $1000.
FYI, you are going to need a Class II Databus interface wiring harness to install any aftermarket radio into your Tahoe (applies to all 03-up GM trucks). These get pricey, especially if you have Bose and/or want to retain your On-Star.