With UV you will need the bigger 12 inch one's,If it was the regular one's you could probably get away with the 6 inch,I have a pair of blue 6 inch cathode's in my case and it light's it up pretty good.
i had 2 UV neons for my reactive ide and floppy cables but they didnt do much at all. i just dumped them when i got 2 blue neons with my fan controller, does a much better job tbh.