I think you should go for it. The potential of the K series engines is well above that of the B series, and the parts for them are just gonna keep getting better. Hondata got 254whp with just an intake, header, and ecu tuning ( www.hondata.com/racecar )

The K20 heads are so much better flowing than any B series head. I think that you would be making a wise decision by going the K20 route. I think if you went with a B then you might regret it later on down the road