Looking to buy a Mustang

Im in the UK, and have decided to buy a Mustang after being in Vegas for 3 weeks, its like Mustang city over there
I really want a car with the new shape around 05, but today saw a lovely 03 have a look
http://users.autoexposure.co.uk/veh...oexposure.co.uk/AETA53529/AETV26395100_1a.jpg

now this has only done 22thousand miles and is just what i want, Auto, Roadster.
but
the new shape really gets me
Is a V8 so much better then a V6? have been told the V6 does not hold its value?
Is a GT much better value then just a standard Mustang?
Also saw this one, this is a 09 and looks stunning but is a load more dosh, and what sort of mileage will i get out of these cars? Have to admit at the moment i have a Crossfire, so if the mileage is better then that will be very happy, i get around 25mpg on the Crossfire
this is the 09 one
http://www.americancarcentre.com/cardetail.asp?catId=380

Any advice will be great, as im getting told all sorts by the sales people.
Also are parts cheap? for mine its all German Merc parts cost a bloody fortune
Hoping to hear from people very soon.
thanks