you don't feel the 6x would be too high for close shots.
i've never looked through 6x so i'm not sure
Here is a suggestion, head to one of the large sporting goods stores which has displays of scopes mounted on demo stocks, set one on 6x and look around the store to see for yourself. Our local Bass Pro has one and I seem to recall them at Gander Mtn & Cabellas.
IMHO a 6x is just fine for 30 yards.