Denon recievers are normally rated pretty well, but I haven't heard much about the 1403. Most of the well reviewed Denon receivers are the x80x series, i.e., the 1800, 2800, 3800, 4800 and 5800 series. Current models end with the "3" designation, which is to say 1803, 3803, and 5803. I don't think there's a 2803 and 4803 yet.
Denon usually rates its power at 6ohms, so its refreshingly nice to see it rated at 8ohms for a change. Full bandwidth ratings simply mean that the power is available across the entire audible bandwidth, i.e. 20-20KHz. So, if Denon isn't lying, you can pretty much except REAL 5x70Wpc RMS. However, as good as Denon is, you probably won't get that much. Its just a rating, and actual power output of cheap receivers generally fall short of their ratings.
As for "350W total", nobody in the audio industry adds up the individual channel power ratings and give it as a total power output rating, you simply don't calculate it like that. Only in the computer/multimedia market do I see such advertised ratings. It borders on fraud, and is just plain wrong.
Anyway, if you have a small room and/or the rest of your system isn't really good stuff, then the 1403 should do a good job. Its a step up from the multitude of HTiBs out there, and is actually quite feature rich. What are you actually connecting it to?