I've got one of the FGSS group buy IRO frames, that are pretty similar to the Angus but made with Deda tubing. Mine has a threaded fork and is drilled for a rear brake (why not?). I think it's a great frame, and I wouldn't hesitate to recommend the company. I just got the frame and fork, then put my own components on it, which is what I would do if I were you since I don't think there's anything special about the components they source and supply.

IRO frame = ~275
Open Pro+Formulas+butted spokes=250
All-City crank+1/8" chain+1/8"cog+lockring=140
Scavenge an alloy seatpost, solid-feeling stem, handlebars, brake caliper and lever from a co-op or the used bin at a LBS (mine gives away that kind of stuff)
I don't know what your preferences are for pedals and seat- I'd go clipless and Brooks, but you'll definitely be over budget with those.

That'd be a nice bike. You want to put the money where it'll make the biggest difference- rims, decent chainring, good solid frame. If you wanted to cut costs you could probably lose the nice butted spokes, maybe cheap out on the cranks themselves and just buy a good track chainring- those things are worth the money up front though, I think.

EDIT: http://www.bicyclewheelwarehouse.com...&productId=194
You can get the wheels for $205, with your cog and lockring. That frees up a bit of money for your saddle and pedals. Do it!