rekn, baggage bay for the 139 is 300kg. Used to be standard 200kg with option of heavy floor for 300kg.
Pretty sure 300kg is standard now and without Aux Tank, you can convert that space to baggage as well for a total of 400kg.
Cruise speed is wrong too. You can cruise as fast as you like in a 139, but without an MVA you won't like the ride above 150. The 1/rev is so low that you feel the 5/rev coming through and it feels horrible. Like driving on cobblestones. Mast Vibration Absorber takes care of it nicely, but at a cost both in $$ and weight (35kg).
At 6400kg, 100% Tq, flying at Vne, it should CLIMB at 500ft/minute. So high speed cruising is no issue for the 139.
145 is just the comfort cruise and will typically be obtained with about 70% Tq.
Just to add, I don't think that MTOW for the 160 is where they will leave it. Expect that to jump by a good 300kg at some point in the future. 139 started at 6400, then 6800, now 7000 and has been tested beyond that.