No to offend anybody using JetPlan, but with only 2 turboprops Jetplan appears a little overdimensioned. I doubt that your AOC would allow ETOPS NAT crossings (so why questioning how the systems behaves across the pond).
Don`t get me wrong, I think Jetplan is a good system, but I doubt that you can place a deal that will justify the cost.
O.k., this will also probably mean that you might have to put up with some hardships as lack of SITA and/or AFTN interaction. However, trust me with only two aircrafts flying (where you will mostly have only one available - due scheduled mx windows), you should have plenty of time to run your plans with a less fancy system and fax your ICAOs to the local AIS office (this will even save you the cost for SITA, which for small operators is quite expensive, not to mention the cost and availability constraints for AFTN).
Also, if you are focsuing on scheduled traffic (low cost???), you will most likely be operating on RPLs and fixed routeings, so there is only very limited need for a full featured flight planning system.
As for cost effectiveness, I heard ( - I stress I cannot confirm this - ) that PPS and RODOS (SAS flight planning) are among the cheaper ones. Well, you say you have the brochures from most operators (and their price list).
Cheers. .fcit