I have a Trek 7100 hybrid. I want to buy a faster - road bike. My main use is fitness - to get into shape - not riding more than 2 hours. I would also like to commute to work. What bike would most suit this type of riding - riding distances less than 25 miles? I've looked at Giant OCR 3W, Giant FCR 3, Specialized Sirrus, Trek FX line. My budget limit is $700. Thanks