So I think I'm finally going to be able to invest in decent glass, and my budget is about $2,100. Ideally I would like to get the 70-200 f/2.8 VRII, and the 24-70 f/2.8 VR. Each of these are about $2000 refurbished... Do you think it'd be worth the risk to get a used one for cheaper (around $1300)? I know I probably won't be able to get both on my budget. But I'm thinking I can get one, and then get a decent prime instead with the left over money. I'm currently working with a D750 and 50mm f/1.8, 18-55mm f/3.5-5.6, 70-300mm f/4.5-5.6. Thoughts?