You would need to use larger needles with the aran, and yes, a smaller size. You may need to go down 2 sizes smaller - figure your gauge with the aran and needles you'll use (probably a 9 would be good) and divide the sts per inch into ths stitches used for the other sizes. Pick the one that's the closest finished measurement you want. Men usually like roomy sweaters, about 3-4" larger than their chest measurement.
The yarn armount would be approximately that for the smaller size, but probably less. I make worsted weight sweaters with size 10½ or 7mm needles and only use about 2/3 the amount needed than if I used size 7 or 8 as given in the pattern. You can do a rough estimate by comparing gauges; if your yarn is about 4 sts per inch and in the pattern it's 5½ sts per inch, your gauge is about 72% of the pattern so that's the percentage you'd apply to the yardage. That comes out to around 6½ 100g balls, or 650g, whatever the yardage is per 100g.