Why not test the new DENON AVR-4310 or AVR-3310 or even a Marantz? Too bad, since these brands are maybe even better then the ones here...
Might be because these amps are not actually available! Just because they have been announced, does not mean the press have access to these new amps for review purposes. Denon UK themselves don't even have any yet!
1) The PS3 is not set to output via HDMI. - Connect the PS3 to the TV via Scart AND HDMI, then using the Scart (coz you can see that on the screen) go through the Video settings on the PS3, and change the video output settings to HDMI. Sorry I don't have a PS3 in front of me right now, so cannot tell you EXACTLY what the options/settings are.
2) Input 4 on your TV is shared. i.e. input 4 could be HDMI or e.g. component video, and you need to go in to the setup of your TV to tell it that when you select input 4 you mean HDMI.
All HD Ready TVs will accept and display 720p or 1080i images, there is no choice to be made. I think what the question is actually saying is should I buy a TV with a native resolution of 720 (usually referred to as "HD Ready") or 1080 (usually referred to as "Full HD"). As mentioned by John this relates to the number of lines a TV can display.
In all honesty the difference is marginal. The number of lines a TV has is only one small ingredient towards making it a good/bad TV. Don't make the assumption that because TV x is 1080 and TV y is a 720 that TV x is better. Also the distance you sit away from the screen also impacts on whether you (and by "you" I mean the human eye!) can actually distinguish the difference!
Remember for the vast majority of the time you will be watching a 576i (standard definition) picture, so a lot will depend on whether your TV's scaler which takes the 576 lines and spreads them over the TV's 768 or 1080 lines is any good or not. It's for that reason I would say whenever you are in a shop looking at a TV's picture to decide whether it's good or not, always ensure you ask to see a normal TV broadcast via the aerial.
Also, remember that at present Blu-Ray (inc. PS3)/ HD-DVD (RIP) is the only way of getting a 1080p signal to your TV, Sky+ HD broadcasts at 1080i not 1080p.