well first of all if you like the ambassador there is a t5 version that you should have got as well. This would likely be the easiest way to maintain your current concept. But if youre going science (and arent thinking to buy the Vesta), you could do one of the following
2 DBB and a torp fore, and turrets aft
2 Cannons and a torp fore and turrets aft.
Science ships turn well enough that I see no real benefit to having turrets fore. Espescially since the science skills youll want to use all have 90 degree forward arcs anyway. Dual beams allows access to the subsystem targeting on science ships, cannons play nice with the turrets for scatter volley or rapid fire.
Also, Phaser relays give a better bonus than prefire chambers. If youre running all phasers, this is a no-brainer upgrade.
People seem to love the mirror RSV (super cheap on the exchange), but the regular RSV or intrepid (or fleet versions of either) are fine too. Depends if youll get more mileage out of an extra tac, science, or engineer ensign.
Keep in mind that youll have less engie skills than a cruiser no matter what, more science skills no matter what, and less hul but greater shields. Therefore, your tactics will naturally have to be adapted. When you get to VA, the Commander skills available that arent available to you right now will necessarily dictate your strategy. So its hard to say how to keep the same concept, as you dont have access to the things that are going to determine your endgame concept yet. You will likely change your mind umpteen times before you land on something you like. And thats a good thing.