WIP right now, but as good a time for feedback as any. Two pages in the works right now.
How to power your arcade cabinet project:
http://beta.arcadecontrols.com/cabinet-power.shtml
Too much space between "search" button and next section. Tighten up some...didn't realize the rest was right down there

Separate the "tip" box with one more carriage return on top and bottom to make it stand out - same with all the rest of the boxes
Maybe try yellow text in warning boxes, and the link kinda disappears with the blue color, make it contrast much more with the black background
Monitor power warning:
http://beta.arcadecontrols.com/monitor-power-warning.shtml
The black background on that page doesn't fit with the rest of the site, unless the rest of the site will be changed over to that same black background
The "Caution" box is almost invisible since it's the same color. Contrast it so it stands out, with perhaps a secondary color for a border too, and change text color there
The horizontal line elements REALLY clash with that page. I don't know if a different color would look better, or a solid color instead.
I like the black page....it seems to feel easier on the eyes, especially with the grey text, but I dunno how the site would look if you unified it all like that.