Your buddy Tom does have a great deal on the IB3800s. $5/cell, that's not bad at all.
I personally like the GPs myself, but IBs aren't too shabby either.
Hard-cased LiPos are quite pricey. The TrackPowers are probably the best out there, but remember, you'll also need to get a charger capable of charging LiPos. You'll also want to make sure you charge them correctly and make sure that you don't under-volt them. Not sure if the RTR B4's (B4 RS) ESC has a LiPo cutoff.
I personally do not like the ESC that comes with RTRs. They are usually just enough for you to run your car but nothing spectacular. If you're just bashing around in the street, they are fine, for competition, they won't hold up...
I would personally save up and get a better radio. The RTR kits seriously lack a good radio. It's still crystal-based, and you'll have to fight for your frequency when you get to the track...
Another thing to save up for is brushless. I've held out on brushless technology until about a month ago. Never looked back since. Possibly the best thing I've ever gotten for my B44...
RIP TAP RC