Forum with email: module comparisons / changeover paths

Hello all

I could do with some advice on Forum modules, and on possible paths between them as the site develops.

I'm building a new site, and I'm on a newbie learning curve with Drupal which means it's going fairly slowly. That being the case, I'm thinking in terms of launching a kind of v1.0 or beta site to be going on with, and adding more features later.

At first, the forum will be a relatively minor part of the site, with probably not a lot happening for the first several months. In those initial stages it needn't do anything that core forum can't supply.

However, at some point a few months or a year down the line, I plan to use part of the forum area to support and document a collaborative project (up to perhaps 30 participants). And ideally, I want the project participants not to have to come to the site if they prefer email. I.e. I want it to function as an email discussion list as well as an online forum - a bit like Yahoo Groups, only not as tediously slow online, and preferably with subscription to individual threads or subforums as well as the whole lot.

(It has occurred to me that I could have one "main" forum for general stuff, and another completely separate one for the collaborative project, but in fact I don't want to go that way; there are advantages to having all the content in the same area.)

At present, I don't think I'm going to want private threads for anything (or at least, I'm pretty sure I could manage without that).

There's no need for the emails to have fancy formatting; plain text will do.

I'm using D6, and I'll probably stick with that as long as it's supported unless there's some compelling reason to migrate to D7 earlier.

So my "research questions" at the moment are

1. What modules would you advise for the forum/email-list setup? (I'm aware of the existence of Advanced Forum, Organic Groups, Notifications, Subscriptions etc, but I could use an overview of which ones would best go together and what they can & can't do.)

2. Supposing I did start off with just core forum for now, how would the conversion/switchover path be from that to the eventual setup? Which are add-ons to core and which are different systems entirely, and in the latter case, is there automated support for porting old forum data and how well does it work?

You can see where I'm going here - I need to decide whether (a) I can reasonably launch with just core forum, or (b) I'd regret having to do the switchover, in which case I really need to climb the "clever forums learning curve" as part of the beta setup.

Thanks in advance for all voices of experience :-)

Jennifer