ok, for starters, ec05 is the sprint distributed rom version, as would be eb13, or eh17 or any other 2letter2number codes on the epic forums. i'd stay on ec05, it seems to be the most stable rom/modem combination. you can flash most any rom (including the eh17 leak) from the ec05 rom, and you'll suffer less reboots or problems (unless otherwise stated by the rom developer) as long as you wipe properly. as you seem to be familiar with rooting, remember to make nandroids at any important step. as far as roms, i like the simply aosp and the cm7, but they have no touchwiz or sprint bloatware. if you like that, try srf.
finally, please be respectful of the forum rules and post in the proper place. this should be in q&a
edit: the 'E' stands for the year, 2011, and the 'C' stands for the month, march. this rom was released in march of this year. EC05 was the last official release, and was froyo. anything after EC (ED, EG, EH) are all gingerbread leaks that are less reliable.
~professional lurker, they call me BEER~