Note on the Marmot Den: I don't know if it's the same tent with a new name (same dimensions and features, but different color) but I bought the Marmot Kronos (4 person)
and over the course of a Grand Canyon trip (we used it probably 15/22 nights) the poles started to develop permanent bends in them (as some of the Sierra Trading Post reviews mention). On a later camping trip, one of the poles snapped entirely. I don't abuse my gear and was even very careful in setting it up to avoid putting unnecessary strain on the poles. Fortunately, Sierra Trading Post took it back.
A friend of mine used the Sierra Designs Wu Hu 4 on the same Grand trip (when he didn't just sleep out) and really liked it. I found it back in the fall on Steepandcheap.com for a really good price, so I picked it up. Haven't used it yet myself but it endured the same harsh conditions the Marmot did on the Grand trip and held up fine.