For the types of things you're in the market for, pedals and saddles are both pretty universal.

It is foolish to order replacement parts for a bike you have not even ridden, especially when it is your first fixed gear. Get the bike, make sure it is properly assembled (take it to a shop if you don't have any bike-savvy friends to call on), and ride it for at least a few weeks before you go "upgrading".
For all you know the stock saddle is the most perfect saddle for your anatomy ever. You can't know without riding it.