I find these to be plenty bright. Shown with 9v... even brighter with 12v source. I'm going to look for the link to my write up. I had written down the radio shack part numbers and the resistors needed for each LED for a 12v source.
EDIT: It's not in the quick reference anymore
I used the following:
Yellow Led Part Number 276-0351 QTY=1 uses 1 560 Ohm (not K) resistor eash. Pkg contains 2 LED's
Blue Led Part Number 276-0316 QTY=1 uses 1 470 Ohm resistor
Red Led Part Number 276-307 QTY=1 uses 560 Ohm resistor
Green Led Part Number 276-0022 QTY=1 uses 470 Ohm resistor
560 Ohm Resistors Part Number 271-1116 QTY=1 (package contains 5)
I do not have Radio Shacks part number for the 470 Ohm resistors, Im sorry! They have um though.
This is a neat link for figuring out the resistance needed.