Upgrading from Macbook Pro. Questions!

Hi all!

I've prioritised a bit and decided to sell my 2010 MBP and buy a new iMac. A few questions!

-This MBP is a 2.6ghz i7 (dual core). I'd like the base 21" iMac with the quad core i5. Is there a performance increase here from my MBP?

-I've noticed the GPU is the same as t he ones they put in the notebooks at the moment. How does this fare for light gaming (World of Warcraft, TF2 etc)?

-I'll be using this mainly for music editing (orchestral, so HDD intensive). Is this a good choice?

Offtopic, but I'm selling my current MBP and I've advertised it as including student warranty (UK educational purchases include 3 years as standard). Is this still valid with the next owner? Do Apple still offer this warranty plan with 2012 purchases?

I hope people can give me some insight Thanks!

 

Yeah I'm not expecting a huge increase in power. I prefer being at a desk and having the larger screen so the desktop works best

 

I'm in the UK and the cheapest refurb 27" is £1,199:
http://store.apple.com/uk/product/FC813B/A

The price I'm getting for the MBP means I can get a base 21" with a student discount and still have a tiny amount left over I don't really want to spend outside of that. Otherwise you could guarantee I'd be getting that big screen!