If you can possibly afford it...
If you can possibly afford it; I would suggest keeping the Rebel and buying a 30D. Two cameras are a wonderful way to shoot because:
1. You can use two lenses which CAN give you top-notch IQ and fast autofocus while having an extremely wide focal range. You don't need to get a wide range zoom which usually is not super in the AF and IQ departments.
2. You do not need to change lenses in the field as often reducing the chance of damage to the equipment and dirt on the sensor.
3. FINALLY, AND MOST IMPORTANTLY, IF ONE CAMERA GOES DOWN FOR SOME REASON, YOU STILL HAVE THE SECOND CAMERA WITH WHICH TO SHOOT! THIS SAVED ME DURING A TRIP TO ALASKA'S KENAI PENINSULA LAST YEAR. I FELL CLIMBING A SLIPPERY SLOPE ON THE FIRST DAY OF THE TRIP AND BROKE MY 40D. HOWEVER, I WAS ABLE TO SHOOT THE REST OF THAT VERY PHOTOGRNIC TRIP USING MY SECOND CAMERA, A 30d.