JockoT - in North America, there is rarely a fuel economy advantage in the "new" top gear. The bottom and top ratios are often the same.
(FYI for JockoT: Pontiac Vibe here = Toyota Matrix. Not sure if you got that model. )
bratboy - welcome to the forum!
If the top/bottom ratios are the same, but the different intermediate ratios let you spend more time in the tallest possible gear for your road speed, there would be a slight fuel economy advantage.
Were you considering going with a numerically lower final drive to reduce RPM? I did that in my Pontiac Firefly (Chevy Metro). Reducing RPM by 25% translated to ~5% better cruising fuel economy in top gear.
http://www.metrompg.com/posts/tranny-swap.htm
here do you do the majority of your driving? City or highway?