The Roman Equites and Sex Suffragia: A Plea for Help

I am looking for information on the Sex Suffragia, a privileged group of 6 centuries within the 18 centuries of cavalry of the Roman voting tribes. It is very ancient and information is hard to come by. Some of the books I am currently researching are these:

• The Roman Middle Class in the Republican Period
  
• The Cavalry of the Roman Republic: Cavalry Combat and Elite Reputations in the Middle and Late Republic

Both have been helpful, but have only served to further my intrest in the very early Servian and Camillan systems of the army. From a military point of view the Sex Suffragia do not appear to differ from the normal equites. However, their place of honor seems to have descended from the earlier equites celeres of the Kings of Rome.

Second to this research, I am also seeking sources on the clear differences, politically, and possibly militarily, of the equites equo publico and the volunteer forces of those who served equites suis.

Anyone who has additional resources in these matters or expertise, feel free to dicuss herein

Have you tried online? If so, what major/expert sites have you tried?

Yes, Ive exhausted all the normal sources as well as JSTOR, Questia, etc. I am basically seeking people here with personal expertise or knowledge of other books I could check out.

In that case, I'm sorry to say I can't help you much...