PSU ignorance

[ural]

Greetings to everyone, I am about to start my first build and retire my old P4 to HTPC (those mules still exist and even sold in Newegg). But before I retire it, I wanna make sure it will run without hick-ups in the long run. Here's what stock 305W powers right now:
Intel 915GRO MATX
Prescott 3.4GHz P4 HT
4x512MB DDR400
512MB HIS X1650PRO (PCI-E x16)
Creative X-Fi (PCI-E x1)
TV-tuner (PCI slot)
200GB WD + 500GB Seagate
1 DVD-RW drive
3 Fans(besides internal PSU fan): CPU, VGA and one 100mm exhaust fan

First of all - is 305W enough in the long run for the current specs?
If yes then I am planning to add more HDDs as needed, and since the PSU has total of 3 HDD power cables, I assume that I can safely run up to 3 HDDs. Eventually it will be 200GB+1.5TB+1.5TB. I am seriously considering putting 2 low RPM 80-100mm intake fans to keep HDDs a little cooler. Given that configuration, will 305W be enough? I suspect it will be close, just wanted the opinion of PSU professionals.

 

[poohbear]

the 12v amperage is much more important than total wattage. Total wattage can be rated as high as 500wt, but the amperage on the 12v rails are much more important info on whether the psu can handle ur rig.

 

[mpilchfamily]

The amperage on the 12V rails relates very heavily to the total wattage. But as mentioned the 12V rails amperage is one of the key things to look at. For your needs your current PSU is fine. IMO you shouldn't waste your time adding more HDDs to that system. I'd save the money and build yourself a new system.

 

[ural]

Thanks for a reply, poohbear and mpilchfamily.
12V amperage is rated at 18AMPs, which I suppose amounts to 216W. Will that be enough?
I wanna keep it as Media Center/DVR in my living room (hooked up to TV), with quite a bit of media stuffed into it. I am not really buying any HDDs now, just planning to add later given I run out of space and the PC is still running. And I am currently building a computer from ground up for primary computing purposes.