John,
Depends on the TV. Lots of TVs give an RGB picture that is way too dark and it's not even as easy as avoiding certain manufacturers - some models from a manufacturer will be ok, others will give a picture that is too dark, so you need to explore particular models. For example, Philips PW6006 has had reports of dark RGB, but Philips PW6515 is fine. Most JVC models have dark RGB feeds. I've found Sony TVs to be the most consistent with RGB feeds - haven't seen a Sony model that gives a dark RGB feed yet. That's probably because they are one of a handful of manufacturers that enable an RGB picture to be fully adjusted (contrast, brightness, colour, sharpness, etc).
If you find RGB too dark on your own TV, you should use S-Video instead.