I ride in those stretch pants, and wear my marmot precip for my top.  No, I don't have fenders... 
  
I have a mountain bike too, and am debating if that will be my winter ride (with thinner tires) 
  
  
I'd get the fenders on whatever you choose to ride, and ditch the precip in favor of something a bit more breathable, and maybe get some cold-weather cycling pants. I think they make some that are waterproof/windproof on the front/ breathable on the back of the legs. Ditto for tops - more wind/water resistant on the front-side, breathable on the sides and/or back. Getting waterproof shoe-covers that extend up to your ankles also makes a huge difference.   
  
You bastards, now I have no excuse!  Except for snow/ice, then I can puss out. 
  
I'm not sure about water proof pants... I don't get too miserable in the stretch pants unless it really pours.  But the jacket needs replaced.  I have the shoe-covers but they are only water resistant and soak up really fast... gotta get waterproof ones this year.