Hi :-)
Thanks for the great shows
The gaming website I write for (as a senior user) uses similar methods as described by hexgrid. Among other bonusses, if you subscribe, you get to see a certain video format two hours earlier than the non-subscribers. You can also do a "one-time-purchase" of 99 Euro-Cent to see it immediately. This could be done for 3MA as well.
Personally, I believe sufficient ppl might subscribe without actual bonusses but just to support the show. Obviously, this would (or at least should) put you in a position where you could maybe communicate how the money is used. I like your idea, Troy, to install a system where ppl can subscribe for a sum of money they can determine.
----------------
Another suggestion: The same webpage asks for donations for specific purposes, usually around christmas, that benefit the webpage and content produce (e.g. a new camera). You could, by way of example, ask for donations for an iPad for Rob or a trip to Firaxiscon or to allow you to make time available to discuss a very time demanding game. You could set the amount you need and ask for donations. If the money donated does not suffice and any excess money could be carried over to the next project. I suggest to not use Kickstarter etc. due to the extra costs involved.
You could even do a poll, e.g.: Would you like us to discuss the time demanding game A, B or C.
This way it could also be ensured that your listeners are actually interested in the time/money consuming topic (well, interested enough to (help) financing it ).
Personally, I would be most interested in more games being discussed, including time demanding games. I am not interested in iPad games (I don't have an iPad). I not that interested in trips to events either. Of course, every person has different priorities and could help funding accordingly.