Bikey Mikey

Remember, this year's Tiagras are generally as good as a 105 components were a couple of years ago.

Gerryattrick

If the top tube is not quite the ideal size, then in order to get both the reach and KOPS right you could try shorter or longer stems.

No substitute though for getting the right size frame when buying the bike.

jimmuller 

First a disclaimer - I'm a regular in the C&V forum. I like older bikes. Take all this with a grain of salt.

Don't rule out steel. Listen to NOS888. The important features about any bike for any long ride, century or not, are that it fit, that it be comfortable, that its components function, and that it roll easily. If comfort is a concern, as it ought to be on a really long ride, choose your tires carefully.

Further disclaimers FWIW, I'm 65. I've been riding for decades but I rode my first century a year and a half ago, I think. I regularly ride distances of 65-75 miles. All my bikes are steel, 70's or 80's. My century was on a mid-70's Masi with 700x23mm tires. Most of my other bikes have 25mm tires, one has 28mm, another has 32mm. Our vintage tandem has 32mm. Any of them can be comfortable.

barrykai

Bought a new 2013 Gran Fondo 2.1 at a big discount since it was last years. Today I did 40 miles and it was the easiest 40 miles I've ever done, however, I'm coming from a Fuji Absolute flat bar fitness bike. It's surprising how big the differences are between the bikes but much of it can be attributed to the aerodynamic advantage of drop bars vs flat bars and the 10 plus pound weight loss. Also, the carbon seems to transfer much more power of my pedal stroke into moving the bike forward. One unpleasant surprise is how much toe overlap there is into the front wheel which will be even worse if and when I move to a longer crank. The other concern is the matte black finish has some carbon fade imperfections that look like water spots. Someone described it as leafing? I'm told that both of these items are normal but I don't have and experience with either.

FBinNY 

$2000 buys a lot of bike. You'd have to work hard to end up with a dog at that price point. Shop a few bikes in the 1.5-2k and test ride a them (bring your own pedals and shoes if you already own them. Pick the one that fits the nearest to spot on, and feels best.

The point here is that good fit and ride trumps whatever subtle differences in the quality of the components.

BTW- unless you have a clear winner at near to 2k, don't blow the entire budget. Shoes, helmet and other stuff can add up to a decent chunk of change.

Also, having ridden many, many century and longer rides, I believe that the one thing that makes the biggest single difference is a pair of well fitting comfortable shorts, so make sure there's dough in the budget for those too.