Either the MK2/R190 or the MK16/390 would work fine; the 2nd stages are identical except for size, and I seriously doubt you'd be able to tell the difference in breathing between either of the 1st stages under normal recreational conditions, assuming the regs are tuned well. The main diffference between the MK2 and MK16 is that the MK2 is an unbalanced piston, about the most simple and reliable 1st stage available, while the MK16 is a balanced diaphragm, also very reliable (but more parts and probably more reliant on regular service) but delivers more air, and keeps the IP stable even when the tank pressure drops to almost nothing. If you're a new diver this may not be the advantage it seems; as an unbalanced piston will begin to increase breathing resistance as the tank pressure drops well below 500PSI, when most divers are exiting the water anyway. If for some reason you forget to pay attention to your SPG, or it stops working, the MK2 will "remind" you that it's time to head for the surface. To be honest, I can't notice any difference in mine until about 300PSI, (I did a little "test" at a safety stop) so the often-made argument that unbalanced regs breathe badly at the end of a dive is only true if you like to run your tank to dangerously low pressures.
The MK16 is apparently being discontinued, which might mean you can get a deal on it. Lots of people like this reg, and it does have the advantage that you could pair it effectively with a high performance 2nd stage like the G250.
