In the UK and looking to buy a refurb 09 27" iMac. Pondering 2 models at the moment, the 2.66 i5 @ £1259 and the 2.8 i7 @ £1399. One thing I'm wondering is if the £140 price bump to the i7 is worth it? What are the diffferences between the 2 processors speed wise? I'm mail going to be using this for streaming HD video and similar multimedia tasks. Thanks.