[cruizerman]

Hey Empire01. The gel filters do not take much of the brightness out at all. In fact, depending on the color you choose to use, you may find that the color is deeper and more solid. Naturally, if you get a gel color like purple of deep blue, it may cut down the intensity a bit.
With the addition of LEDs, simply match the LED color you want with a matching colored gel. If you are adding red leds for example, use a red gel to help mix the light from the existing soldered-in bulbs with the LEDs.

Adding LEDs to the 03-06 cluster is not hard, because there is a large open area between the back circut board and the face of the gauges, so you can drill holes in the sides of the cluster and insert the little LEDs.

The easiest way to do the LEDs is buy them on ebay where they are already wired for 12V because each one has a wire pigtail with a soldered on resistor. All you do is hook the wires up to power and ground!

Good luck!