i think if you really set ur mind on P90, why not save towards that goal?
getting a D2 in between, would just cost you more in terms of money and time ....
if you get a D2, you may be saving and waiting for P90 to come along and perhaps drop in price ....
then why not wait for the time being and straight shoot up to P90 when the time comes?
if you have D2 that time, you would need to re-sell perhaps reorganise your system, etc .. and may end up losing 1k or more ....