Best one in the system right now is two years off probably. Bill Rhinehart was a 2007 11th rounder and tore up Vermont last year. he is doing the same thing in Hagerstown and leads the South Atlantic in several categories. He is hitting over .340, has 7 homers. Doesn't obviously help now, but keep your eye on Rhinehart because I think he is going to catapault up the prospect list.
I agree with you here... Bill is also leading the league in RBI's, althought his stats aren't as high as you mention. I think the FO sees Chris Marrero as the 1B of the future, and I heard they may try Bill in the OF in Potomac or Harrisburg in order to keep his bat swining for the Nats. Whitesall was a loss, but with talent throughout the organization at 1B, it's not a huge loss as long as one of these guys wins the spot and produces. I hear Boone will be the 1B de facto, however, while Johnson gets everything looked at.
Broadway - at 27, let him go or trade for a pitcher.
Lefave - serviceable - possilbe Nats backup. .244 AVG / .353 SLG needs more production and more time in the minors
Marrero - at 19 he shows promise, but a lot of playing time between now and the show. Good power, but more consistency. 5HR's / .220 AVG / .386 SLG - his fast start has been slowed down
Rhinehart - 23 years old. Nothing has slowed this guy down yet. .326 AVG / 6 HR's / 39 RBI's / .553 SLG