Can I upgrade from Sony Str DE197?

I have been thinking about an upgrade for sometime now and I finally have the means to upgrade my 2 channel stereo system. I run the Sony thru a pair of Axiom M3V2 bookshelf speakers and a Yamaha YST SW216 Subwoofer. I am eyeing something in the $350- $500 range. Are the new Yamaha, NAD, Cambridge or Onkyo integrated amps worth the change or would I end up feeling like I just wasted money. I understand that I'd have to get a good tuner as well but thats another concern. I can play my iPod touch and stream FM radio for now.

 

I guess another way to question this is to ask, "how good is the amp section of the Sony compared to the options (the Yamaha, NAD, ect.....) I posted above. Can I do better