Richer,
I don't remember numbering of any Eheims by heart (including all those I have

), but it can be easily found on the Net or in a catalog. If you cannot, let me know, and I'll find the manuals of mine and figure out the model numbers.
You may get the smallest Classic. No, it's not self-priming, it doesn't have any trays, and it doesn't come with shut-off valves (you can buy them separately). But once you start it, you don't need to shut it off until it's time to clean the canister. If the intake is at the bottom, only a complete water change will make you to restart the filter.
The Classics are much less expensive than the modern models, and I'm sure you can buy them used on Ebay. Naturally, Professional series (esp., Prof II) are much more interesting and sofisticated and convenient, but for the tank of this size it's hardly makes sense to pay more.
As for the media, I use all my canisters in the same manner: fully filled with ceramic noodles. Most of them have regularly cleaned sponges over the intakes. In this configurarations they last for many months without any need for cleaning. And when I do clean them (every 6-12 months), I do it only because I want to remove the gunk, and not because the filters stops or the flow drops noticably. That's why my 6-12 months in some filters can be 12-18 months, depending on how lazy I am.
