Pioneer vsx56txi or vsx74txvi.Which sound better?

I have the 56txi,and looking to upgrade to the 74txvi,for the hdmi and other connections.But I am worried that it make not sound as good,as the 56txi since it is 10lbs lighter,and rated at 140 watts.Sound is more important than anything else.Has anyone compared the two.I have the M&K 75011 speakers .Thanks .
i am in the industry from sales to installs.the 74 has a 9 band eq that will adjust room corrections and even make lessor speaker sound outstanding.they will add punch to the highs mids or lows .will do phase(not to be confused with polarity) corrections and eliminate standing waves.the 74 will calibrate what the ear cant hear.the input instructions in the manual are vague.if you have little experience on set up, your comman sense will not help me if you have issues setting up the hdmi switching.
Thanks.What makes me leary about the upgrade is.I went from the 45tx to the 56txi,and was disappointed with the 56txi sound.The 45tx seemed to have more power,even though it has a lesser rating,Also the 45tx seemed a bit brighter than the 56txi.Is pioneer elite trying to bring the cost down and in the process,also the quality in there newer models.Is the 4 series still the best.Thanks