Is this power suppy good enough?

I have a 400W PSU that shows the following numbers on the side. Will it be able to support a mid range video card properly? I have a Athlon64 3000+, MSI RS480M2-IL mobo, Transcend 2x512 DDR400, Seagate 80GB SATA, NEC ND-3500A

+3.3V 28A
+5V 30A
+12V 20A

My monitor takes power from the PSU. Does this power come from the total 400W that the PSU can provide or is the 400W power of the PSU independent of the power supplied to the monitor?

the power feed to the monitor is a straight pass thru, no effect on the PS 400 watts
the brand of power supply determines whether the amps you quoted are real or inflated

Even if it’s a truly crappy brand, generic 400W PSUs which can, maybe, deliver 300 are still good enough for most systems.
I can’t remember where I read this, but someone tested a current computer in a worst-case power consumption scenario and it came out to only want 250W.
Pretty much any PSU is good (power-wise) for a current computer, provided you don’t stack it with drives. If we’re talking quality, though, that’s another matter.

So shifting from a CRT to an LCD will not make more power available to the rest of the system?

No, afraid not.

The 12V, 20A is the main factor. The A64 3000+ is less power hungry than an Intel Prescott, so there’s probably enough in reserve (if the ratings are trustworthy) for a midrange card with a power connector.

I just checked it, and my PSU is a L&C. The review site says that it only provides 17A on the 12V rail. Will I still be able to run a Radeon X1600Pro on it?