lapdog, these guys are right on with the .25-06 or .260. The .243 is Ok but I watched more than one antelope take an 80 gr .243 in the chest and take off to another county. Oh, it killed him but not real quick. I really like the .243 and killed alot of deer with one but I wouldn't use anything less than 100 gr bullets.
I think the .25-06 would be a fantastic choice as would the .260 or .257 Roberts. Get one of these and you will never have to buy another rifle again as you got one to take just about anything that walks (yeah right).
My favorite all round cartridge for deer and antelope is the .270. It shoots plenty flat enough and packs enough punch.
As for scope, your Leupolds are good. If you like em, stick with em. I would get the ballistic plex though. I like the one on my Burris fullfield II.
As for rifles, sthick with what your most comfortable with and fit you. You might want to try out one of the new Savage rifles with the accutrigger. These are pretty neat.
My friend got one an few months ago and we can't in .30-06 and it shoots everything good, and really likes Sierra 180 gr boattails.