Tough call....I would risk trying to get another QB at a lower price. Brees, Brady, Rivers & Rodgers should put up roughly similar points this year that it is worth saving the dollar or two so you can spend more elsewhere.
Now I caution you, if other teams are already keeping QBs this leaves a few QBs left and the price for guys like Brady, Rivers and Brees might be higher than you originally expected. If your league is anything like mine, owners that already filled the QB position will bid up the price or maybe you'll get a bargain, you never know with auctions. Simple economics