if you want to learn more about bikes i'd buy a nice frame and move over whatever you can from the purefix. do some research to figure out what parts won't switch over, because you'll have to buy some stuff. But that way you can see the differences with the frames and learn a lot. Then down the road you can do the same with wheelset, crankset, pedals, etc. You'd learn a lot about bikes and get to pick exactly what you want. plus you could do it slowly, allowing you to spend more on a nice frame/fork/headset if they rest of you parts you can switch from the purefix.

If you couldn't give two ****s about learning anything about bikes or don't have the time and just want a better bike, then just go buy a better bike. You get more for your money if you go used off of ebay or cl usually, but if you want new there are a lot of options if you have $1000.

Wabi Cycles Special fixed gear bike specs
someone will probably tell you to get that.