for wm6.5, i like this one:
http://forum.ppcgeeks.com/showthread.php?t=67673 . you are just going to have to try them and see what works for you. on 6.5 you may also need to try some of the memory tricks...disabling the camera and changing the page pool size. you can use the search function to find out more about those work.
if you find 6.5 to not have enough free memory, search out some of the dcd 6.1 roms.
did your phone come with a micro sd card? i use the included 512mb card to flash stuff.