Separating PCR products on agarose gel with similar bp length

[umwong25 from cc.umanitoba.ca]

Hi,

I am trying to separate 745bp, 646bp, and 655bp fragments on an  
agarose gel. I've separated the 745bp fragment but the other two  
fragments are not separating on a 2.5% agarose gel, running at 55V for  
3.5 hours. I also want a crisp band because I am planning to cut these  
fragments out and extract the DNA for sequencing. Any suggestions?