In the meantime the 6i will be fine for less contest'y type models and flying tasks. Gliders descend quite nicely with just flaps or spoilers for landing control when you're just looking for a way to steepen up the approach or get back down from that killer storm cloud thermal. Crow may be needed for contest models but for general fun flying there's no real need for the extra drag it provides when you're not trying to spike the model to the exact second and inch.

Even for the models you're considering if you're not going to actually fly in a contest or if you're willing to accept a slight penalty and just try to compensate for it by flying with more control you can do fine without crow. But if a first place is what you're after then when it comes to that point you will want to buy a new set to go with the new super slipper sailplane.