I agree with DGarretson on the nude Vishays. I've been buying mine from M Percy. However, if you need a greater than 0.5W power rating, then Mills non-inductive wire-wounds are favored by most. These come in 2W, 5W, and 12W power ratings. The Mills are first rank for plate resistors in tube gear. For >12W, all bets are off. I also agree with Doug that the Rikens have a certain charm, if you want to add a pleasing coloration. I would not use Rikens exclusively but rather mix them with Vishays et al. The second most transparent resistor I know of is the Caddock TF020, but alas these are only rated for 0.3W. Caddock MK132s and Caddock power resistors are also top drawer. Kiwame is in the mix, but be aware that you can buy Kiwames under another brand name for much less money; see the TubeDIY Asylum for info. I forgot about tantalum resistors as sold by Angela Instruments. They go up to 1W rating and are available in only a limited number of values, but they are also on par with the Vishays, yet I can hear a very tiny difference between the two types, which probably means that neither is totally transparent.