Victor:
I don`t think you need a regulator for the 6 volt batteries you`re buying.
I fly an 87 inch YAK with the DA50-R and in-cowl muffler. For a plane like this you should look for digital servos or at least some good quality coreless servos that have 160/180 oz. torque. I have not seen a pattern ship in the size you want, but there are a lot of IMAC planes for that size. With the digis, Imac plane and the DA50, you will be closer to $1800 or a little more.
One question, are you going to fly only pattern? or mostly IMAC? That will make a difference in the kind of plane you should get.
Just my 2 cents.
John