I think the ultimate steelhead combo, will be a double handed rod. While it takes a little bit of time to get used to, the fishability of a spey rod well outweighs the time to learn how to fish them a little better....it's all about line control, and a double handed rod will out-mend and in my opinion more importantly out fish (with less effort, there is no wear on your body) a single hand rod. You can still make 100 foot casts, even with very little room behind you, and the real beauty is you can mend maybe 60-70 feet, instead of the 30 you might be able to do with a single. The only downside is you would have to step up a reel size to fit a spey line of the same line weight on it Depending on what time of year and where you're fishing, the line's get a little quirky, but they're truely not that hard to figure out if you give yourself some reading material.
The TCX is a cannon, and i've had the chance to fish the single and the spey, and they're truely amazing rods. Super fast action, so you can cast it a mile. I have the 4500, and they're great as well.
If you're looking for an amazing spey rod, look no further then the Sage Z-Axis, they're almost always being consistently reviewed as the top spey rod out there lately.