there is knewton online which is pretty good as per members here .. and they have money back policy ...
and I am personally towards gmaxonline.com who have a free sample and the videos look interesting
With the money you save on online course you can buy more tests or material for GMAT.
I personally felt MGMAT/KAPLAN
classes a waste after going to the sample class of all. Not at all wort the money. So try knewtown (frer for 14 days) and gmaxonline.com (has sample video )