Well, you don't have to switch off the norms for knobs. You can use hybrids. Or you can use norms all around and play with the suspension. But you guys are making it sound like you can't maintain rev with XRG in a drift, or even drift with the XRG at all which isn't true. You can setup an XRT to lose speed in a drift too (whilst applying full throttle). Does that make the XRT underpowered? Even the XR3 will have that problem. But hey, is 300hp not enough? I wonder... Oh right, the car is on slicks. It may feel underpowered for you guys because you're used to the bigger powerful cars, but for someone who hasn't been there before won't know the difference. For someone who simply wants to enjoy a little drifting, doesn't necessarily need to buy S2 (though I'm sure everyone would recommend it).
As EVO said, there are many things you can do to your car to make it more drift happy. Typically, you want to only change ONE thing in garage. If you make more change, how do you know which one made a difference?
1. Less grippy rear tire compounds (Hybrids work fine too)
2. Increase rear tire pressure (not too much either)
3. More rear toe-out (-0.1 initially)
4. Increase rear anti-roll bar stiffness (just a few clicks)
You can also try applying the opposite to the front which would have a similar overall effect (ie. grippier tires on the front - norms)