A computer I'm upgrading has an inexpensive Enlight case with a 250w
power supply, so I've got to at least upgrade the PS. It's a
mid-tower case, but I have no idea if it would accommodate a newer
PS, as it's not as deep and wide as my own Antec Sonata case. Should
I look for a new ATX case with a decent PS or just put a new PS in the
Enlight case?

I figure a newer case would be better for airflow and front USB ports
at the very least.

The PC is going to be running a P4 3.0c 800fsb Northwood on an Abit
IS7-E motherboard. I'll use its onboard audio for now since we're
starting out with those little Dell speakers that attach to the
bottom of their LCD monitors, but I may put the SB Live! to use
if/when we upgrade to a powered 2.1 or more setup. At first only one
hard drive will be put in but I'd anticipate up to 3 HDs in the
future. It'll also have at least a DVD-ROM and DVD-RW drive, a
Radeon 9800Pro and a wireless NIC. How many watts do I need to power
that configuration?

I love the Antec Sonata (380W of quality power) I have for my
computer, so I'm quite an Antec fan and I'm wondering if I should
just get another one or if the new 450W Sonata II
http://www.newegg.com/Product/Produc...82E16811129155
would be better? The other two I'm thinking of are the 400W Antec
Solution SLK3800B
http://www.newegg.com/Product/Produc...82E16811129163
(says it's a rackmount case (?)) - and the 400W Antec Performance
TX640B
http://www.newegg.com/Product/Produc...82E16811129157.
Any preferences among these cases? Anything I should be looking out
for?

Thanks!