I would recommend the biggest fuge that you can fit in your setup. A 6 gal fuge is on the small side, but if that's all the space you've got, it is better than none.
I agree with jt48. Extra precautions should be taken for stuff outside. Especially, the chiller is hooked to a delicate reef system. Besides, vandals, there are plenty of uninvited animals (big and small) come visit us every day and night. On top of that, after a few hot summers, the PVC pipes...
Phosphate promotes brown film algae big time. I have to use phosphate remover to keep it in bay. IME, dry food contributes the most of phosphate in my tank.
I like Exotic which has good prices and huge selections. Yourreef is another coral specialty store I visit a lot. They have plenty rare coral to chose from.