Ok, you are on the right track but note that your stem and bars must match. I suggested 31.8 and Dunbar 25.4 which is correct, but as he suggested, match them.

The link to the stem is a little confusing due to the picture. If you want aggressive, I guess you want to be lower. The angle of the stem is important. That's the tricky part. If you want the stem flat, you need less degrees. For example 0 deg / 90 deg. These figures are usually the same angle depending on the manufacturer. One in your link was 130 deg...with that, you would be worse off.

Go to a shop and look at them and picture them on your bike. Many bikes have different steerer tube angles so that's why you should go look feel and picture them. Now, on my bike I went for a 20mm riserbar, which may or may not suit you. My guess is somewhere between 0mm (flat) and 20mm is your go.
Dunbar's suggestion to get a 25.4 bar first and try the angle first on your current stem, is the best idea. I only suggested 31.8 because I like the look. If you bought a 31.8 first, it wouldn't fit on your current stem.
Sorry if I'm confusing the issue here.