cyclists-a help question for you.

[Lionheart]

I'm currently riding on a Toys-R-Us $69.99 special-for the last 5 years. It works for keeping in shape and riding along with my 10 year old and his friends, but I'm thinking about getting serious about cycling, especially with a bike-a-thon fundraiser event coming up in April. Any thoughts about the 2007 MOTOBECANE le CHAMPION SL ? Saw it on ebay, and other sites for about $1200. Never heard of it before, but I have heard of Trek (thanks to Lance and the tour-de-Lance), but they seem outrageously priced, although the motobecane seems a little stratospheric as well. I do realize that bikes can easily cost 4 to 6 time more than even this motobecane model, but it does still seem excessive to me in my currently ignorant and uneducated view. Is this something I should spend that kind of money on? I spend a ton on my photo equipment, but that lasts forever and a day. My cheapo bike still works well, replaced the tires once, patched them more than a few times, but is heavy (28 lbs) and clunky compared to my business partners $2700 bike (don't recall what make/brand, but I do remember it weighs in at 17 lbs). Is it worth the extra $1100 to buy a bike like the Motobecane or a similar Trek model? I ride maybe an hour at most with my kids, usually on the hills of my neighborhood, sometimes we drive out to the American River and ride the trails there for about 20 miles. I weigh in at a hefty 150-155 on a 5'7" frame if that helps anyone.
Thanks in advance.
Leon