Yeah, I checked the prices... just under $1000 for a 2-bunk sleeper. On the other hand, there are a bunch of round trip flights for less than $300.
Looks like I'll be flying through the air in a sardine can.
Honestly thats probably for the best. Sure they say its 26 hours but Amtrak has terrible on time ratings west of the East Coast. You'd probably be on the CA Zephyr with an amazing 34% on time rating. Hell AA to Chicago is only 57% on time
http://www.washingtonpost.com/blogs/wonkblog/wp/2014/07/10/the-sorry-state-of-amtraks-on-time-performance-mapped/
If you're flying out of DTW then I would look at Delta and Southwest. United has some nonstop flights there too but in a tiny\cramped 2-2 seat config CRJ-200. Its also a United Express flight which typically has a much worse on time rating than Delta.
I think most delta flights are on the MD 90s which is nice if there are two of you and you can snag the right two seats as the 90 is a 2-3 configuration. There will be the occasional 737-800 on this route though which is the traditional 3-3 config. I think the seats are slightly narrower on the 738 as well.
Southwest runs an aging 737-300 in the morning non-stop. With 100% on time its fine mechanically but the interior will be worn and its unlikely to have wifi or free TV. The non-stop in the evening is a newer 738 with wifi and likely free TV if that matters
If it were me I'd try for the MD 90 on the 2 seat side price depending. Also remember if you use the Big Blue Lot and fly on Delta you'll need to take the shuttle to the McNamara terminal. (Pretty much everyone else is out of the North Terminal which is connected to the Blue Lot) There is parking over by McNamarra but the daily rate is expensive $21 vs $11. My company won't pay for the difference so Blue lot it is for me. They typically run every 15 min or so
Edit: I forgot to mention that overhead storage on the MD 90 might be an issue due to smaller overhead bins. The plane will likely be louder as well. Delta's 738 on this route doesn't currently have seatback In Flight Entertainment but they are upgrading those planes. Depending on when your trip is it might have been upgraded and may include a fairly substantial inventory of free movies to watch in a back of the seat screen