Do not dismiss the auto without at least driving one. It truly is an excellent drive. Having owned both in TT form I would now choose an auto over a manual in most cases. It has such a smooth yet ferocious power delivery that it never fails to make me grin.
However, if you have had to work out your running costs down to as fine a point as how much you will be able to spend on fuel each week, then in my opinion you might be better off holding out until you can comfortably afford to run one properly. They really are not an economical car to have on the road, and as soon as you start 'modifying' then thats when it will really put a strain on your pocket.
If serviced PROPERLY you will have no major headaches with it, but even a standard service can run above '' normal '' prices. My advice if you do decide to go ahead with one, is always pick quality and maintenance over the toys! happy shopping