Do they also make the ultimate 2m/440 for a base?
If not; then who?
My vote for the ultimate omni would go to something like the telewave 8-bay dipole array, with a Stationmaster (decibel systems I think) after that. Lots of money tho ;-).
I have a Diamond X-510 and like it quite a lot though it won't really take high power well (over a couple hundred watts). Considering most other people don't run much power, it works out well anyway. Not a lot of use talking farther than you can hear people calling you back.