The bike WILL make little difference.

Guys nowadays are climbing the French Cols on 16# (or less, see Saeco) bikes in times pretty much approximate to what the peloton climbed them in during the 70s and 80s on bikes that weighed about 20#.

If I get blown out the back of a group riding hi-tech bikes while I'm on my steel framed Colnago or my even more retro friction shifted Basso it's b/c I can't spin my pedals as fast as the group. The reasons I can't do that have to do with my physical conditioning not the fact that their bikes are a lb or 2 or even 3 lighter. In cycling the engine is paramount. Lance or Ullrich still ride like Lance and Ullrich even if Trek and Bianchi decided to switch to "retro" steel frames. Even for a very fit 15olb rider 2lbs is a pretty insignificant percent of the rider/bike package.

When young and reasonably fit I had success on my 27-28lb Motobecane against the then top of the line 21lb racers. The weight difference there is more than anything today.

Buy the bike YOU like unless someone is sponsoring you, then ride what they give you. Probably not since you're here asking advice. I like lugged steel frames so that's what I buy. Though I bought and still have a first generation C'dale in 85 or 86. If you truly like an alum. bike you try then buy it and ride it. Don't worry about the rest.

As an aside. in my experience the "yuppie" bike riders described above buy Litespeeds or USPS replica Treks.