You should be able to get a very nice bike within your budget, about US$ 2500. For this amount you should be able to get a carbon fiber frame, Shimano 105 components, and Mavic Aksium wheels. All of this is really good stuff that will work well and work reliably for many years. The Aksium wheels are bomb-proof. For an example, take a look at a bike like the Giant DEFY Advanced 2. But, don't get hung up on brand names. The bike business is so competitive than any two bikes at the same price point are usually equivalent values. One way to get more for your money is to find a shop with one of last year's models left over. Those bikes are often discounted to get the bike off the sales floor. The issue here is finding a bike that is your size.
Road biking is a different world. Personally, I found that switching from mountain bikes to the road as my usual ride had me emphasizing endurance more than short-term burst strength. There is a basic change in rider position, more leaned over to be aerodynamic. The bike is lighter, smoother, faster, and more efficient. You will spend much longer times in the saddle than on a mountain bike. For that reason, small adjustments in fit are more important on a road bike. That's why you should only buy from a bike shop that knows how to fit the bike to you. Your road bike will give you lots of different hand positions which is valuable for long rides.
Test ride the bikes. Go to as many shops as you can and ride whatever they have to offer in your price range. Buy the one that fits and feels the best regardless of the name on it. That is the bike you will enjoy and ride the most. Riding a road bike that fits you well is a joy and a pleasure. Riding an ill-fitted bike can be torture even if it is the latest and greatest all tricked-out US$ 15,000 Pinarello Dogma 60.1.
HTH
