Front light doesn't have to be as powerful as back light, since it doesn't have to cut as hard (Par 38s keeping up with 250w arc lamp from behind for example).
Not sure where the statement that washes cost more then spots comes from. An Accu Wash 250 lists from $1200 while an Accu Spot 300 lists for $1500. Washes are generally a little cheaper, do to less moving internal parts (things like gobo wheels and prisms).
Will a 250w wash keep up with a 250w spot, yes and no. A wash has a softer, bigger light then a spot fixture. So the spot fixture will always look brighter. Keep in mind however that a wash fixture washes and a spot fixture spots. you want your spot fixtures to cut through your wash fixtures, otherwise you can't see them. 4 or maybe even 2 Accu Wash 250s will blow away 8 Par 38s. And the Accu Wash 250 is most likely the cheapest wash unit you will find. If you are set on movement, you will spend some money unfortunately.