Thanks. But this question has already been answered sooo many times by other smart assess (myself included).
To reiterate, here's what I've decided: flip flop fixed/fixed hub (personally, I like the Phil Wood track style hub), with a Surly Dingle 17/19 on one side because those cogs will give me a lot of skid patches if I decide to do skid stops and they will give a nice gearing I think. A White Industries Dos ENO on the other side of the hub with a 20/22 cogs to give me a lower gear for different riding conditions. Currently I'm using a stock 54t chainring but it is super tall, so I'm considering dropping down to a 50/48 double. Which should give me four different gearings with a straight chainline: 50/17, 48/19; 50/20, 48/22 but I'll have to move the axle slightly in the dropouts.