All GT's are basically the same with the only differences being engine choice (obviously), Larger front discs 330 mm on the 3.2 V6 and Cloverleaf as apposed to 284 mm on all other models although the stand brake are awesome anyway. Q2 fitted to Q2 versions only and Bose sound system. These are the only upgrades available apart from obvious wheels and trim colour. Mine has sports seats which unless you are 8 stone and can squeeze yourself through a letter box are pretty uncomfortable.
My advice would be find a GT you like the look of, make sure it has had all the history and has had the cam belt and water pump done if its due. Take it to autolusso and get a Quaife or Q2 differential fitted for £650 then get a remap done by one of the more reputable remapers for £250-£300, there are lots of threads on here. Anything up to 220bhp with much better power delivery than what comes from alfa as standard and better mpg. By looking for a standard car you will have much more choice and it will be around £2000 cheaper than a cloverleaf, leaving you with around a £1000 to spend on upgrading the awful standard head unit for a nice double din one and any other goodies you might like to add.