To clarify, one thing that I meant was that if you want to know what people are discussing in a megathread, you have to go to the end first, then go backwards to find the comments everyone is responding to. You can't just read a thread title and see what the conversation is about once there are 500+ pages.
Regarding the stats I see posted above, I would expect a few threads to show up in that top 10 list. I suppose that the lack of those in the top 10 is also a bit of a symptom of this kind of megathread mantra.
I would better describe seo width as the # of keywords that you are able to rank for.... rather than ranking #1 for something big, you can rank for 1,000 different smaller subjects and get more traffic. Cast a wide net.
Here is some casual advice about ad stuff you brought up.
If you want to tweek ads in the fall, I would tweak the one at the bottom first because that won't be a big deal. Use their giant horizontal ad down there. I forget the size but its about 2x as big as the 768px one and it definitely makes more money. Maybe consider using that big one at the top too, but I would not use 2 at the top or replace the logo.
I would not replace any of the radar stuff. I think people like that, Google knows people like that, stats seem to show people like that, you can trust that you are being rewarded for that in ways that are direct and indirect and I would leave it all there for sure.
The new posts page might be helpful here but I think I prefer the main forum page most of the time. I load this site from a bookmark folder that includes lots of other forums, so they all open at the same time and they all sort of go to the same generic place in the hierarchy. In a higher volume forum, the new posts page just wouldnt work to get an overview... you would want a new threads page maybe, but Id still probably prefer the main page.
"What websites have a good setup for this"? You are asking about the email subscriptions you mention? Not sure, I usually unsubscribe to everything if I have the chance. I know all of the Vbulletin forums do a good job with offfering options but I dont think you need to change anything about email subscriptions. Maybe I am misunderstanding what you are asking here.