If you are used to running 5min/mile pace for 10 miles everyday, then Im guessin youre gonna be a pretty darn fast cyclist too. I'd spend the extra cash and get the nicest thing that you can reasonably afford. My first bike was great for about 6 months, then I started riding more seriously and wished I had waited and got something better. In my mind I dont find it very hard to justify bike purchases..."Its for my health"...thats what I tell myself at least