Is the harmon kardon avr 225 receiver hi def? we had a "non" hi def tv hooked to our receiver and we are replacing the tv with a hi def LED. do we need a new receiver?

It does not have any of the usual HDMI or component video jacks on the back. The highest 'def' video it supports is S-Video (standard def).

http://en.wikipedia.org/wiki/S-Video

It is NOT necessary to route video through an audio device. Your TV is the ultimate and most logical first recipient of any high def video content.

Whatever video you elect to pass through this thing is not modified in a good way if at all. You COULD just run the HiDef video straight to the TV and not have to worry about what could be happening in the excessive and unnecessary cabling that takes it for a trip through the receiver.

The receiver can still be managed by running its composite (standard def) video from the Monitor Out to a composite input of your new TV.

Likewise, no digital audio would improve from passing it through any device that just acts as a stepping stone to the receiver and ultimately your ears. That iswhy all decent A/V gear has provisions to run the signals separately to their optimum electronic end-user.