Hi there folks, I posted this in the road bike section and several people suggested I'd get better answers in this forum.

I had two questions for those who know vastly more about bikes and biking than I do. I'm a newbie, just started and have been trying to commute to work. I have a long (20+ miles each way) ride that is 90% on a river bed bike trail, so I don't have to go on the road much, I also have a locker at work so I don't carry anything but repair items. I don't race and haven't gone on any group rides, nor do I expect to do either in the future. However, I do want to ride as fast as possible to cut my rather lengthy drive time down.

My question is, would I benefit from a better bike, would I experience a noticable increase in speed? Currently I ride Schwinn Fastback 27 I generally find myself spinning at 95-110rpm at the 42x19 or 42x17 gear ration (mattering if I'm riding with or against the wind), would a more expensive bike such as a Trek Madone (or another bike is the same price range ~$2000 [the 07s are on sale]) ride noticably faster, or is the speed increase only really noticeable in a race where a small increase in speed would make a big difference. I realize the biggest variable is my motor, but would a nicer bike make a noticable difference? I'd be thrilled if I could average over 20mph, currently I go 14-15 mph and figure I can eventually strengthen my legs to go 18mph on my schwinn. Would a nicer bike give me a 3, 4, or 5 mph premium; would I ride at a higher gear ratio, or would I just spend money to spend it (I'm fairly satisfied with the schwinn)?

Basically are the returns on an expensive bike worthwhile for someone who has no intention of racing, but wants to get to work as fast as possible.

Also, I wonder if better bikes are built for racing, are they more fragile for day to day use? For instance, lighter tires sounds nice, but will I need to true the wheels every couple of rides (My route does have some rough areas, but overall is fairly well paved)?

Thanks in advance,
W