I think you should buy the ones you like and can afford. The cheaper the gauges are, the more money you have for other stuff. The cobalt series is hella expensive compaired to other autometer series. I can't justify spending $200 on a cobalt series oil pressure gauge when I can get a pro-comp version for $60. (optauto.com pricing for this example.)

I will personally stick to the black face pro-comp series. Not expensive, and with the right bulb color, will match my orange cluster lights. As long as it works, I don't care.