Yes, many retail stores do not have higher end items on hand in the store, but they can be ordered for you. It's safer than buying online.
Also, consider Best Buy as the ordered items can be returned to ANY store location in the country. Buying online mean doing a return online.
I believe you will need a 64G SD car to record 4K video. Most stores will let you test it out.
If 4K video is your primary interest I'd also check out the Sony AX53 camcorder. By tax laws camcorders have some features SLRs cannot.