OP, this is the best advice I can give to you at the moment. I strongly support SR. Was here for over a year before the disaster that took place. But, right now SR is not the best option for buying goods. They have no User feedback base for a customer to rely on. And, as you stated, the BTC values are incredibly innaccurate. I am not raging against SR, but to be blunt, they need to get their shit in order. Honestly, the launch was too soon. But no one is more to blame than us for that, we demanded a new market. And we got it, bugs and everthing. So, my point is, until things get ironed out on SR, choose Sheep or BMR. It's hard for me to do, as a loyal SR member. But, the rates at those markets are fair, accurate, and updated reguraly.
For the time being, my suggestion is to shop elsewhere(it sucks saying this).
-T