Going nuts trying to find the right bike for road and track!

earthwatch

I currently commute 30 kms 5 days a week and have been doing so for a year.
Im really enjoying the challenge of going further and faster and constant improvement is what keeps me really motivated. Going further is the easy part ie my #1 aim is to increase to 50km plus this year. Going faster is another issue and my feeling is that i would like to step upto a faster bike. My current bike is a scott P3 and I avg 28kms. Im really happy with it but just dont feel its helping with my speed aims. I have looked at the Kona phd, Scott speedster fb30, Scott sub 10, Jamis Allegro 3, Avanti and trek. And all seem to offer good FB road bikes. However my dilemma is that I want to get a bike that I can also use on weekends as I do longer road rides (100 to 150 km) and rail trails ie mainly warburton track (70 to 100km). I figure the best way to deal with this is get a FB bike that can take wider wheels ie min 28 (although im not certain if this is the solution ie these might still be to narrow for dirt tracks). I would greatly appreciate hearing from anyone that has similar riding objectives and how they have managed to deal with road and dirt track needs. Cheers!