you have a very interesting search in front of you. The spey market has exploded in the past few years and there are so many wonderful rods available. A great deal will depend on what you want from your rod. Do you like fast rods or slower? Do you tend to fish very heavy tips or lighter ones? Do you like to shoot line with a short head or do you want a longer belly? As you will see mentioned on here and other sites you need to take a bunch of rods and lines for some test drives to determine what fits you best. If you haven't cast a two hander before I would recommend you hook up with your local spey guy or find a good casting instructor. Trust me it will save you lots of money and frustration in the long run.
While I now live in BC, I grew up fly fishing the Great Lakes and have some experience with the rivers there. I would agree that you want a rod between 12-14ft that casts a line weight between 6-8wt. If I had to have one rod for the GLs it would be the sage 8136. This rod has some guts and will cover most situations you will encounter. BF mentioned the 7136 which is one of my favourite rods. Unfortunately sage discontinued that rod for this year. If you like slower action rods like me then thats an awesome rod and there are still some around.
All my spey rods are sage. Yes there are tons of rods that are just as good if not better depending on taste but there are many that aren't even close. The reason I buy sage is the incredible customer service that they have given me. Just last fall I broke my 7136 two weeks before a big trip to the Nass. I shipped the rod and called them to explain my situation. For no extra cost they had my rod rebuilt and returned intime for my trip. That and several other experiences like it have made me a sage fan for life. The warranty is not the only reason I use these rods. I think my rods cast very well...and they'd cast even better if I was a more proficient caster.
One direction I would recommend you investigate is the Skagit style. Rio and Airflow are comming out with Skagit lines this year. If you spend most of your time with tips its an amazing way to go. While I have not cast them yet I've been told the new GLoomis rods are amazing. They allow you to throw heavy tips while using sporty little rods that are a blast to fight fish on.
I wish you luck in your search. You will encounter many different opinons that are all very valid. You need to see what fits you.