I had the GT series (GT-54 and GT-30) and sold the back panniers. Too big and heavy, too many pockets. I got the T-42 and I'm very happy with them. My only disappointment was that the T-42 use smaller zippers than the GT series. The main compartment is almost as big as the GT-54. I went on a small tour and carried tent, sleeping pad and bag, two change of bike clothes, two of normal clothes (one short, one long), rain gear, stove, fuel bottle and mess kit, tools, maps, some food, toileteries and a camera tripod. Everything goes inside the panniers (tripod attached outside with the revovable pocket straps). The large mesh pockets are extremely handy for drying clothes/towel and for things you might need quickly. I stuff the rain cover there and a baseball cap when I don't want to walk around with my helmet on.
As for racks, Tubus are great. I have a Logo. My front carriers is an old Man Mountain AC low-rider and it feels cheap compared to the Tubus. I'm sure I'll change it for a Tubus Tara sooner or later. The nice thing about the Tara is that it doesn't get in the way of removing the front wheel. The Surly Nice Rack looks nice too (low and high position with platform) but i'm not sure they're available yet.
In short, you should be happy with your choice.