[josephlord]

Specifically on the processor it may be cheaper to get the base and replace it immediately for £1800 [1] than to buy the top of the line than to pay Apple the £2800 extra it seems to ask for what appears to be the same processor (cache, speed at least). And you might be able to sell the original.

[1] http://www.scan.co.uk/products/intel-xeon-e5-2697-v2-s-2011-...

[MBCook]

If I'm going to drop $5000 on a computer that's not meant to be upgraded like that, I'm not going to immediately take it all the way apart and risk ruining it to save $1400. I would either pay it or not buy the upgrade.

[josephlord]

I wouldn't either (would probably just go for the cheaper one if I was going Mac Pro which I am not) and the 8-core might be the better upgrade anyway looking at the Anandtech review.