Re: Seating Question..
Depends on what you consider "upper level" and from what vantage point you'd prefer. I've sat in 600's and 500's (prefer the 500's) and in both sections was in the corner of the endzone. I liked it being able to see the plays develop down the field.
I sat one time in the 100s (I think it was) approx 35 yard line about halfway up, it was nice and all being that low and close to the action, but if the play wasn't in front of my area, I was watching the plays on the big screen. Meh.
Sat another time club level, mid-field.... meh. Too uppity.
If you're ready to dive in for season tickets, give the HT.com field animator (or whatever it's called) a whirl. It'll give you a pretty good idea. If your not quite sure yet - get a few single game tickets in different areas and you'll see what works for you view-wise, fan-wise, and sun-wise with the latter being a big point when the roof is open. 500's and 600's never had the sun on me and the a/c was close by that I wasn't sweating it out with the roof open.
Only thing about 600's - it's pretty steep (500's is a bit as well) but I wouldn't go too far back in the rows of the 600's.
Lastly, if you can swing it - try to get on the side of the stadium that your parking lot is on. Saves a little hike time.