Sony's amps should not be any worse than competing brands. Where Sony lacks is features, and namely its room correction system appears to be way behind the curve.
Having said this, Pioneer's room correction does not equalize low frequencies, and from what I understand, Yamaha also doesn't do much in that department. The problem with this is that the lower frequencies are where equalization is really needed.
Now, this may not matter much for your room or equipment.
Frankly, I'd upgrade the display first and then worry about the AVR (which may also diminish the need for video upconversion, since most displays nowadays do a good job of it.)