So, the blackjack tables were kind to me this last weekend in Tahoe and I now have $700 to spend on a second bike (for which I've been in the market for a while). I'm definitely going with a fixed gear and want something pretty nondiscript looking since it will be my commuter/city bike so I want it to look low-key and not be more of a target for theft than necessary. However, I want something that has a nice ride, a stiff frame, track geometry, with decent components but room to upgrade.

I've had the usual Kilo TT in the past - upgraded the wheels, tires, saddle, pedals and bars and loved it. I'm probably going this route again (raw frame on BD, add an open pro/forumla wheelset, standard MKS pedals, decent saddle, I already have some track drops) but wanted to see if there are alternatives that I hadn't thought of. I need to stay within budget with or without upgrades. What is another good frame (preferably unbranded) to start with that would still allow enough cash for decent wheels, etc.? If you had an extra $700 what would you do?