potential new owner, option "package" question

Hello,

I am seriously considering buying a 2011 Tacoma V6 TRD OffRoad Double Cab. Over the past two years, I've been drifting back and forth between buying an HD Diesel, a domestic 1/2 ton, waiting on smaller diesel rumors, etc. etc. etc. I started looking at trucks by picking the Tacoma in late 2007. Now I'm back to it, and getting ready to do the deal.

I think the Tacoma is the most capable, reasonably-sized truck for daily use, utility use and responsible (casual) off-road use. I know there are wild to mild mods out there, but I'm done with that scene (ridding myself of a lifted, locked 01XJ with a money pit's worth of mods)

Now to my questions/confusion:

Is it correct that you can't get the JBL audio upgrade with Sirus/XM in the double cab? The package picker won't let me do it, at least not with the off-road and v6 tow packages selected.

The Toyota package picker is a bit of a mess, it seems, so what's the obvious difference in the two I'm missing? (What's OBCT?) I'm sure it's a noob question.

TRD Off-Road Extra Value Package $2,870.00
TRD Off-Road Extra Value Package OBCT $3,035.00