Having been to a few stadiums myself, including: Neyland, Ben Hill, Michigan and Oklahoma Memorial, I find the 100,000 range to be a great atmosphere. As much as I hate UT, and I do truly hate them, the large and somewhat intimidating stadium is somewhat of a nice place to visit, besides the creme-sickle orange. Michigan had a dead crowd for the most part, not as loud as I would have expected. Ben Hill-Griffin was against Vandy, so it was not as loud as it could have been. OU was the only other large stadium I've been to.
I would really like to see Alabama eventually expand to over 100,000, with the other endzone being added on to. I believe it would be difficult with Paul Bryant Dr. on that side and the cemetery beyond that. But with both ends closed in it could trap alot of noise and make Bryant-Denny an itimidating place to play. Sure it doesn't rise right over the opponent like at UT and FU, but the noise could be undearable for the opposing offense if this came to fruition. We may well see this one day, since in the last 12 years we've seen the stadium expanded three times (around '94(i believe), again in '98, and currently).