All your choices are good, but...
I'm a biased Castro Valley fan. Steel frame, same as the Volpe, with a 1X9 gearing and a very smooth, gentle ride. The knock on the bike is the gearing. With the standard cassette the low gear is a pretty large 43 inches. (See Sheldon Brown's website for more info about gearing).
I had the LBS change the rear cassette to a Shimano 11-34 range from the stock 11-26. The low gear is now 31 gear inches versus the stock 43. In English that means when I'm trying to get up a steep hill one rotation on the cranks moves me about three feet less than the standard setup - enough to keep my cadence up without getting me dog tired.
I disagree with the naysayers about the front light. In a suburban area a 3 watt light is fine. Enough to light up in front of you and unless you're going 25 MPH you won't outrun it. The Shimano light on the Castro Valley also blinks a very bright led constantly whenever the front wheel is turning, giving some added protection in traffic or cloudy conditions - two big pluses when commuting.
Unless you plan to avoid rain fenders are a big plus. The Castro Valley also allows wide tires (700X28 standard, but you can go to 32-34) that provide a softer ride and still allow for pretty good speed.
Geared with the optional cassette , along with an upgraded stem (needed more height), pedals that don't require special riding shoes (a plus when commuting to the office and you don't want to carry extra clothes), a small underseat storage bag with a flat tire kit, and a rear red LED blinking/adjustable light, the LBS charged me just a bit over $650, and he did all the installation of the new parts and fit the bike to me.(He took back my factory cassette and stem, but let me keep the stock pedals). All that and a full Shimano drive system (yes, the 105 has better parts and tolerance, but for commuting the lower end Shimano is the best value out there - real metal parts built from a quality manufacturer. Try to find that on a low end SRAM system).
I can't think of a better deal anywhere given the quality of the overall bike, and the care that went into blending the basic components at a reasonable price point. Lots of people will suggest that the Volpe is the better bike - maybe, but 9 well placed gears works fine for me, and with one chainring I have less problems shifting. The Volpe is also the "hot" bike - meaning discounts are rare. The Castro Valley hasn't been a sales success (not enough gears?) and is readily discounted. Setting up a Volpe will cost several hundred more than the modified Castro Valley, and you still have the same exact frame when you're done. The Shimano front hub/light is about $60-90, the fenders at least $25-30 (Freddie Fenders).
It's your money, but don't dismiss modifying any bike you find in a LBS. The few extra dollars you spend can completely change the value of the bike for you. Good luck.