There are basically two types of home contents insurance policy. One type (with higher premiums) pays out on a 'new for old' basis. i.e. the insurance company accepts that you'll have to buy new items and pays out the current retail price.
However, 'standard' contents policies (with lower premiums) only pay out the 'value' of the items lost. So, if your �2400 TV is a year or two old, it's 'value' (i.e. what you could get for it if you advertised it for sale) might only be around �1000, so that's the amount the insurance company would pay out in the event of a claim.
You should check the terms of your policy to see whether it pays out on 'value' or on a 'new for old' basis. If it's on value, �600 seems to be perfectly adequate. (The value of most PCs falls by at least 50% over 2 years). Even if it's on the basis of 'new for old', the insurance company only has to pay to provide you with a PC of a similar quality to the one which you had originally. They would be failing in their duty to the shareholders of their company (and therefore acting illegally) if they paid to provide you with a computer of a better quality than the one you had originally. (i.e. it seems perfectly reasonable to provide you with a PC with a CPU which has a 2005 specification, since that's what you had originally).
Chris