I finally dug up an old thread, no thanks to this myopic search engine. The old thread had the words "Antec" and "Truepower" in it, but the search didn't turn it up. Neither did Google, oddly enough.
Anyway, some data for you:
Antec Truepower 430W:
"Soft-off state" = 0.12A
Idle at desktop = 2.10A
Power factor while idle = 0.69
Prime 95 torture test = 2.54A - 208.20888 Watts
Power factor during test = 0.70
Seasonic Super Silencer 460W:
"Soft-off state" = 0.07A
Idle at desktop = 1.33A
Power factor while idle = 0.96
Prime 95 torture test = 1.67A - 190.46016 Watts
Power factor during test = 0.96
Not even 20 watts. Now then, assuming 24/7 usage, and maybe.....8 cents per kilowatt hour for electricity:
.208KW * 24hrs * 30 days * $0.08 = $11.98 per month
.190KW * 24hrs * 30 days * $0.08 = $10.94 per month
Savings of about $1.04 per month, if I did all that correctly.
I suppose I could have just done .208 - .190 = 0.018 and multiplied that by 24 * 30 * 0.08 for the same answer in fewer steps, but, you know....my mind is like x264's multipass compression I guess. It needs several passes to get it right.
So it will save power, but it won't really do anything to your power bill. You'd get more benefit by turning off the PC at night. But I do always like things which are efficient.