How bright a bulb can I use?

I’d think so, I have always used brighter bulbs in many lights, 100wt. in 40–60wt. lamps, etc.
Never had an issue but I don’t leave them on for hours while gone or anything extreme.
The LED lights out out less heat than the old standard bulbs so I think you could ramp up the wattage.

The reason they don’t want you to use the old style incandescent bulbs over 60w. is because of the heat they generate, and the subsequent fire danger. Nothing to ignore!!! So, yes, you can go brighter with the new CFL or LED type.

Absolutely! Put in the bright bulbs. As long as the draw is less than 60 watts each you are golden.

Yes, you can use the brighter bulbs.
I think I have some 120w bulbs in a showcase that’s probably not rated more than 40w. It’s on at least 12 hours a day, 7 days a week and there have been no issues.

As stated above, it was the heat that was the issue.

You can, as the reasons for that limit are heat and amperage. CFLs get a little warm, but nowhere near as warm as incandescents, and LED bulbs are cool, so half of the danger is eliminated. And since voltage is constant and wattage equals voltage times amperage, the lower power draw reduces amp draw and thus won’t burn up the wiring. From a safety standpoint, you’ve got a lot of leeway and can go up a few notches.

That said, I find the lumen/watt ratio in CFLs and LEDs to be a bit too high, which makes it hard to get just a little brighter. If you go out and get yourself a couple of 12W LED bulbs, you’ll have more lumens than many car’s high-beams, which may be a bit more than your basement needs depending on how big it is. Since 12 isn’t much higher than 9, you may find that the next step up is a bit much while not having any real options in between too dim and too bright.

You could safely put in something like these 54W LED bulbs that are brighter than a 250W halogen worklight, but that doesn’t necessarily mean you’d want to. Just be aware of how much difference in light 1 watt can make with LED/CFL bulbs before going hog-wild and accidentally turning your house into a tanning booth.

Menard’s has a great lighting section, with a lot of variety and many lit bulbs that show you what you’ll actually purchase.

The color temperature of the bulbs you buy can be as important as the wattage in my opinion.
This is glaringly obvious in my bedroom, where one pull on the ceiling fan chain lights 2 Halogen bulbs. 2 pulls and you get 2 CFL. 3 pulls and all 4 are lit.
Then you carry your shirt out into the other room, because none of the choices show what color it truly is.

@jerv It isn’t all about the hot bulbs melting or burning the wires, there is a fire danger! I replaced a kitchen ceiling fixture and although it plainly said to use no more than 60w. bulbs, someone had replaced the 60w’s with 100w’s. The sheetrock above the fixture was totally disintegrated due to the heat and the wooden joist securing the unit was charred absolutely black! SOMEBODY was really lucky there wasn’t a fire! Can’t say the same would happen to a lamp so what you said could easily apply there.

@kritiper Yeah, I may have understated the danger of hot wires and neglected to mention the possibility of taking the house with them as they burn out. I probably should’ve mentioned that “overheated wires” means “potential electrical fire”, so good catch. Same with the ability to an incandescent light bulb to ignite flammable objects (like the house they’re in).