ColinG - 8:13 pm on Feb 11, 2010 (gmt 0)
I would first move my DNS to a low-cost DNS provider ($30 or so a year) so you would have ultimate control over changing the target ip when you are ready. This type of service will also allow you to set up a sender id txt record that may not be easy to set up elsewhere.
I do not have one in mind. Perhaps someone else will recommend one. Speed of DNS will contribute to speed of site.