I should note: the more people you have in the game, the better everybody's connection needs to be (and the better the host's in particular, needs to be). On TWC/Comcast standard I've routinely had 4-player games with no lag, even with the host also hosting voice chat. You can probably have 8 players on a similar sort of connection, but you'd want someone other than the host to have the voice chat server running.
The players that are not the host have much less requirements in terms of bandwidth, so they should be the lower connections if possible, but in a huge game even the slower DSL lines might get bogged down and cause a little bit of lag (depending on how much is going on at once). For the non-hosts, download speed is more relevant than upload speed.
Anyway -- you should have a great time, just thought I'd mention these caveats since you would be playing with people you might not know, and you'll want to adjust who hosts, etc, accordingly. And someone with a lower connection speed might not be the best idea to include in an 8-player Internet game since they might drag it down for the rest. The host can tell who is lagging the most, if anyone is, by how long the little "(WAIT)" message pops up next to each person's name. If one person has that up a lot, get them to shut down any background upload processes they have, make sure they are on a wired connection instead of wireless if possible, etc.
Also, the players from over at the RelicNews forums are also planning to try to get together a regular Saturday game. I don't know how exclusive their group is, but you could ask around over there if you want: http://forums.relicnews.com/showthread.php?p=3543999
Happy playing, and let me know how it goes!
EDIT: Oh, and when I'm talking numbers of players above, I mean numbers of HUMAN players; not counting the AI in that since there are always two of them. And when you guys choose a difficulty level, don't up it because of having extra players -- the game scales for that automatically. If most of you play on 3 or 4 by yourselves, play on that same level in multiplayer (unless you want even more of a challenge). If you are used to that level and then up it to 7 or 8 (or, god forbid, 9 or 10), you'd be in for a nasty surprise.
EDIT 2: Here's a post on optimizing your multiplayer experience, just in case you do run into any issues: http://arcengames.com/forums/index.php?topic=74.0