in my view, you're taking a GIANT STEP BACKWARDS- the 550 you currently have will do everything you want and more- even if you do go to weighing each load and adjusting the powder to meet the same weight- and it's simple enough to just leave the button out of that stage or remove the hopper so you don't charge with powder on the press- i've always found the 550b to be adequate, even with the issued charge bar, but i'm no precision shooter
and if you're just using your 550b for just one caliber , you're SHORT-CHANGING the press- the ONLY fault there is with the 550b is a lack of AUTO-INDEX , but that's no fault if you're using it for rifle
there's CONVERSION KITS for almost every caliber out there with the 550b- it's just a matter of changing the shelplate and dies- the 45acp, 06, 308, 8mm, and a bunch of others all have the same head so there's no need to change plates, just pull the pins and slide in a different dieplate and hopper- takes all of about 30 seconds
if you have to change the shelplate, that takes about maybe 5 minutes