Okay, I'm not versed on this as well as some of you, so I thought I'd get some expert opinions. The system is:
Intel D946GZIS motherboard
Xeon x3230 (C2Q Q6700 equivalent) running at 2.67Ghz (95W TDP)
4GB RAM
GeForce GTX 750Ti (with PCI-E power connector)
Turtle Beach Santa Cruz PCI sound card
1x 500GB WD VelociRaptor
1x 1TB WD Green
1x rear exhaust fan
1x cpu fan
1x DVD-RW
1x 3.5 floppy

I believe those are all the power drawing devices

The two PSU choices are:
Antec Neo ECO 400C (400W)
+3.3v=20A
+5v=20A
+12v=30A
-12v=0.8A
+5vsb=2.5A

Xigmatek NRP PC-402 (400W)
+3.3v=24A
+5v=15A
+12v1=20A
+12v2=20A
-12v=0.3A
+5vsb=2.5A
edit: the two 12v rails have a max combined power of 384W (32A)

Antec has one 30A 12v rail while Xigmatek has two 20A 12v rails (max 32A combined). Antec has less 4A on +3.3v, but 5A more on +5v rail.

EDIT: I picked the Xigmatek due to the slightly higher 32A combined on the 12v.