The Galaxy S2 that you linked there is a nice phone.
Physically it is VERY light, feels a bit lightweight in my opinion and a bit plastic-y ... very slim and almost don;t realise it is in your pocket it's that light
The newer Galaxy S3 is a step up, better spec phone, more money though.
I dont know if you mean you have no current contract or dont want to sign for one and looking for an unlocked phone only?
The S3 might be out the budget.
I don't think there are many/any phones that beat this in terms of overall performance.
Xperia Play, the Playstation phone, has obvious merits if you into gaming, the physical controls are unrivalled.
I have this currently and loving it, it is on the heavy side but my previous model [LGO3D] was also a bit weighty so for me its no problem.
The screen size is pretty much standard as on most phones these days running Android.
Battery life is good.
Galaxy Note, this is a nice large screen, for things like your web browsing and YT etc it is a pleasurable experience on the larger 5" screen.
Currently on Play at just under 400 down from 700 quid
http://www.play.com/...ne/Product.html
You might find these within budget in other sources, ebay and such.
If you looking to play the Android Market [now called Play] games, you will be ok with the touchscreen for most of them.
If you looking to enjoy emulation, you really need to ensure you get one that is supported by the ICP or other B/T control pad, though ICP is the nicest IMO.
OR ... get the Xperia Play with the built in Playstation buttons.
Emulator playing is a pain with pure touchscreen, I'm sure most people will confirm this.
Your Galaxy S2 is nice, fast, teamed up with an ICP it would be nice.
Setting up ICP is not as easy as using the Xperia Play though still.
Plus you would obviously need to carry the ICP around with you at all times so it is to hand when you fancy a spot of SNES gaming or whatever.
Custom ROMS are available for most Android devices, XDA-Developers forum is the place to check out for that stuff, no matter what model you get.
If you not planning to Root, look into which phones/manufacturers update to latest versions of Android OS ... as LG, for example, are pretty slack and only recently upgraded some of there phones to Gingerbread, which is a joke tbh seeing as it's very old already.
Manufacturers like HTC and Samsung tend to be front of the queue and make updates available soonest, expect them to be pushing out Jellybean soon enough on most their newer models.
HTC have some nice models too, the ONE X for example, but this goes for around 300-350 typically.
Again a touch out the budget.
The Galaxy S2 is a good choice, although very lightweight they do use Gorilla Glass
see
http://www.corninggo...ts-with-gorilla
which makes the screen very strong and not likely to scratch easy.
I've had a couple handsets with this and never used a screen protector on any of them.
If you looking to enjoy emulators on a regular though, I still have to recommend the Xperia Play over it.
The web browsing experience isn't 'that' much a difference yet the gaming side of things is miles apart
PS:
If you really new to Android and not aware of 'Home Launchers' even ... look into them.
Even without Rooting your device you can make the phone look a lot nicer than the standard home launcher that is built into your phone.
I use the 'GO Launcher'. Check it out on YT you will see plenty vids showing it off, some very nice animations and great widgets for it and themes.
There are plenty to pick from too, Launcher Pro, ADW Launcher, SPB Shell ... all good