No you don't do CIMA over the other two - CPA or CA is needed if you want to get anywhere nowadays as an "Accountant" - I'm fairly sure you can get free CIMA membership once your an estabalished CPA (not sure about CA) - definitely don't look to go for CIMA first as either way you won't be a true management accountant until many years of experience, including a wealth of other issues which i won't bother mention cause I'm sure the point is clear enough.