There is nothing wrong with aluminum racks, tubus are just better. My co-worker has taken three cross country trips with no problems with an aluminum rack. She has also done many 2 and 3 week tours. Another co-worker has traveled the world only using aluminum racks. He has traveled from Alaska to Ohio twice, Ohio to Costa Rica, and traveled through Tibet, Russia, South America, etc. He hasn't had any problems.

Since you are planning to do credit card touring, you won't be carrying too much and I think any rack would be fine. I like the Topeak and Blackburn racks. I also like Axiom and Civia racks. The only thing I don't like about the Blackburn is that it doesn't have a light mount. My Topeak Explorer is about $40-45 and if a fine rack. I would have no problem using it for a loaded tour, so it would be fine for your credit card tour. The Topeak you mentioned has had good reviews, but I don't have experience first hand. I would assume it would be a great rack also.

You don't need to spend the money for a Tubus to get a good rack, it is just that if you do, you will have a rack that will work wonderfully for a very long time. I have one Tubus rack, it is great. My other four racks are aluminum. I have no fear of them failing any time soon. Even if one is used weekly on my grocery getter and daily rides to work for the last four years. I have also used it on short weekend trips, fully loaded.