I'd go with Onkyo, but I'm biased...
However, check online for prices... go to the Onkyo site and get a list of authorized internet retailers (there's only about a dozen)
Check the prices/shipping at each one... should be able to shave off a significant portion.
authorized internet dealers
Most have ads such as "WE WILL NOT BE UNDERSOLD"... I went with SoundCity from NJ... they ended up out of stock of the model I wanted and I had to wait quite a while (I contacted Onkyo and Onkyo confirmed the problem was a national shortage of that model)
Best Price Audio is having a special (they always do) with free shipping on Onkyo home theater products. I believe Sound City and Best Price Audio both have the TX-SR501 for $250 -$260. AND you don't have the hassle of a $30 rebate. Plus, you're paying tax (most likely) on the 300 which is another $xx. As far as tax online... I guess that depends on how you feel about whether online purchases are taxed or not, and if they're not taxed whether you should feel obligated to pay the tax to your state.
J&R have it for under $250 with free shipping also. I wonder if the $30 rebate at CC is a CC rebate or if it's through onkyo.... that would make it $220 after rebate if it's through Onkyo.