My long range gun started as the Remy 5R. It's a great gun. I had great luck with the 175 SMK and the Hornady 178 A-Max as well. I've never shot the 168 so I can't speak to those. I'm sure that all three would be great.

If I recall (and it's be a while), the 168 dies somewhere around 800-900 yards. The long range bug can bite pretty hard. If you even think that you may want to shoot to 1000 yards some day, you might as well start with the 175's. I don't see any point in spending all the time and effort to find a good load for the 168's when you will could end up switching to the 175's in the future. I'm not bashing the 168 at all. I'm sure it will serve you well at 500 yards.

In my opinion, just start with the 175's. Good luck which ever direction you go. It's a blast.