All depends on your observing habits. IMO, there are only a handful of objects that the 17mm would be more useful on than the 13mm Hyperion/Stratus. 13mm is great for deep sky and barlowed it's great for planets. More detail than the 17mm. The 21mm would make a good companion to the 13mm for framing some of the bigger objects. But none of these realistically fit the budget of $200-300 given accessories needed besides EPs. Did I mention Telrad!
Film canister collimation is feasible but masochistic IMO.
