Video Connections to TV or AV Reciever?

Hi All,

I currently have a DVD player connected to my HD-ready TV via component video and analogue stereo sound, and PS2 and Sky video/audio via scart. These 3 components all have digital outs which I intend to connect to an AV receiver and 5.1 speaker system (which I haven't bought yet!). If my TV has all the video inputs I need, is there any benefit in routing them through the AV receiver?

In the near future, I'd also like to upgrade to Sky HD, and an upscaling DVD player. My TV has two HDMI sockets, so would this affect the decision to go the separate video and audio route?

And just one more question, would a PS3 upscale DVDs, thus negating the need for a separate upscaling DVD player?

Many thanks.