According to the EIA/TIA standards, there is no 'big E little e' type thing. What you are hearing is manufacturers hype.
We often hear it referred to as "minimally compliant" Cat5e, meaning that it does infact meet the specifications. After that, you have manufacturers making statements that it is good for 350Mhz, or 500Mhz, or whatever. All that is very dreamy, but the fact is it is still only Cat5e compliant.
Good Luck!
Daron J. Wilson, RCDD
daron at wilson dot org