I've got a Touratech VP45 tank bag with side bags. I went for this, initially, because Baglux told me they weren't going to make a tank cover for the 31 litre tank option on the Adventure (ironically, they've just Emailed me to say they now are making one!).
I'd had a Baglux system on my Pan European & been quite impressed. The VP45, however, is excellent. Very well made, it fits together very well and the side bags have the added benefit of keeping the rain & general road crap off your knees and lap! The waterprooof cover only works on the main bag but is very effective. The only modification I've made is to replace the metal hooks on the lower straps on the side bags with a clip together 'dog collar' type connector which I join just behind the front shock. You also need to get a saddler (unless you're handy with a needle & thread) to cut and hem a hole in the base plate to gain access to the filler cap (it's made for a variety of bikes, the hole is ready marked & is not a great drama to cut)
The map case is a separate item and will fit either on top of the bag or onto the base pad. It is also a much more user friendly shape & size than the Baglux one.
Hope this is some help,
MikeO