Thought about a TKX yes and it is a good option - it is a tad smaller, lighter, and a bit cheaper then 6 spd. But I liked the ratios of the 6 spd better and wanted the two over drive gears. T56 Magnum has an outstanding reputation and is known for its shift quality and durability. But I have seen youtube reviews of TKX and people really like how it shifts once they get it installed.
So it boils down to personal preference TKX or T56 Magnum. I would look at gear ratio options between the two, consider size and weight differences, look at price differences, consider which would work best for your car and how you plan to use it ect and decide.