Bike Forums - Back in the Saddle

After a long hiatus, I'm riding once again. Last year I bought a used Cannondale CAD3 Team Saeco (with Dura Ace) off ebay. I wanted to test my committment to the sport before spending a lot of money. I have a Cannondale mountain bike (which I love) so I thought - why not? For $750 it was a great deal. Now that I know I'm sticking with this, I need to get a bike that fits and is comfortable. The aluminum frame of the Cannondale really beats me up on long rides. In fact, I'm black and blue from yesterday's ride (oops! thats because my back wheel came off!). Not to mention the bike is way too big (54 cm when I should be riding 50 cm). The problem is, I don't know that much about bikes. I used to rely on my ex for information (when he wasn't my ex) but that's no longer an option. Back in the late 1990's I rode a Trek 5500 and loved it but I want to investigate other bikes before going back to the Trek based on familiarity. I really want a bike that is going to be comfortable mile after mile after mile. I'm facing 40 in a few months (better than ever, of course) and I'm not able to take the miles like I used to. Ten years ago, I would have said I wanted a bike that was fast and faster! Now I want something that has a comfortable ride even if I have to give up acceleration and speed. Money is not really a barrier except that morally I'm having trouble convincing myself I should spend $5,000-$6,000 on a new bike (I looked at the Odanata by Seven). I also looked at Cannondale's new carbon fiber bike and at least as far a appearances go - its hot!!! Realistically, I would feel comfortable spending $3,000 but I'm not sure what decent bikes are in this range. Any help whatsoever would be greatly appreciated. Thanks!!!