I can think of couple options here. You could load your 30-06 with some lighter weight bullets to get some flatter trajectory, like say some streamlined 150 grain bullets. They will do just fine on an antelope. I think upping to a 7mm magnum for an antelope is a bad decision, I don't believe the recoil in a 7mm magnum is much more than a 30-06 really, should be about equal. You only gain about 8 inches at 400 yards, give or take depending on bullet. I would look to the 25-06 myself. I think with a streamlined bullet, you will actually be shooting an inch or so flatter at 400 yards with a 25-06 than a 7mm magnum. The 25-06 recoils very mildly but packs more than enough energy for antelope and whitetail deer at any range you will be hunting them at. This cartridge gets overlooked a lot and doesn't have a huge selection of factory ammo. But it is down right flat shooting and lethal on anything up to and including the whitetail deer. I know people even use it on elk, but I won't get into that argument. I think your 30-06 is an excellent elk cartridge already and unless you really just wanted to get into the magnum rounds, you don't need anything bigger than the 30-06 for elk.

The 6.5mm (.260 caliber) is an interesting caliber for you also. Using a 130 grain bullet you get about the same sectional density as a .30 180 grain bullet. This means as long as it has the velocity, it will penetrate pretty much the same. The .260 didn't do all that well in the commercial world unfortunately, but is a great cartridge too. Long range competition shooters have been using the 6.5mm for a long time due it interesting balance of ballistic coefficient, velocity, and mild recoil. A cartridge that is being brought to life now is the 6.5-284. There are a few factory rounds out there for it and it will shoot good out to 400 yards, a little less flat than the 25-06 though.

I think the 25-06 will be right up your alley.

Federal and Black Hiils load a 100 grain Nosler Ballistic Tip
Federal also loads a 117 grain Sierra Gameking BTSP

Those loads would be perfect for some antelope hunting where shots might be long.