I made a similar mistake years ago. Bought the 959DX for the mobile and the 2547DX for the base. (Same board). Oddest thing in the world, you could be on frequency one day, then the next day be transmitting on 27.384. Or 27.387. You just never knew, and it didn't relate to warming up. Room temps in the house were constant, and I had probs with the base unit just the same as the mobile.
I later got a little smarter thanks to some good advice from folks on forums. I picked up a clean Grant XL with a Digi-scan for 125 bucks. It had already been tuned up correctly, and still works great to this day. I have since added another Grant XL to the collection, and a Cobra 139XLR base. None of the problems that I had with the Galaxy rigs. I have a friend that I talk to regularly on .385 lsb and he uses an Icom 746Pro, and he always tells me that I am dead on frequency with the Grants and Cobra. And they don't drift, either.
I am new to this forum, but I can tell you these guys aren't pulling your chain. Best of luck with your decision!
73,
RT307