The question of studio lights has come up before. 

In one of those earlier threads, I suggested the use of a Smith-Victor KT750U Thrifty Basic Kit. 
 
After speaking with a tech at Smith-Victor, he told me that the KT750U was limited to using 250 watt bulbs.  He suggested using the KT1000U Thrifty Intermediate Kit which takes a 500 watt bulb. 
 
That KT1000U unit could use their 621920 bulb or an EBW 500W 120V Daylight Photoflood Light Bulb. 4800K.
 

The Smith-Victor tech also suggested the use of a Rosco filter to correct the light from the softboxes you already have.  You would need to contact them to get advice. 

--Martin