New CPU - Advice on PSU please?

Okay, so here's my rig as it stands now:

Asus A8N-E mobo (24-pin power)
Athlon64 3200+ (Venice)
1GB PC3200 DDR (2x512MB)
Inno3d 6600GT PCIe 128MB
Antec SP PSU 350W (20-pin power)
1xDVD+/-RW
1xIDE HDD 7200 60GB
Up to 2xUSB devices drawing additional power

All about 18 months old now, running fine, no problems. (Yes, the mobo has a 24-pin power connector, but just has the 20-pin plug in it - the separate 4-pin one is also plugged in).

Due to the recent dry-up in socket 939 CPUs, I thought I'd grab a dual core to keep this rig up to date for a couple of years yet. I managed to grab an Athlon64 X2 4600+ (Toledo) which is sat in front of me, and I'm now - kind of sheepishly - wondering if my PSU is up to the job. The difference in TDP between the two CPUs is 43W).

I've checked out *this* online calculator, which makes me feel reasonably cosy by giving a requirement of 258W. But the googling I've done seems to show many people with similar rigs opting for something quite a bit more powerful (like 550W).

Now I realise that when I upgrade my gfx card and memory (probably this time next year), I will almost certainly need a new PSU anyway to power that on top of this CPU. But do I need one right now? And what are the risks of just giving it a go? Will it just not turn on? Will I fry the PSU? The mobo? Myself?

My gut feeling is that I'll be very near the limit for this PSU, and that it will probably work if I give it a go. And that I may have problems under heavy load. Thoughts?

A 500W psu is probably about the standard now.
I would always go for the higher rated psu - it can't harm your system as it will only ever output 12 & 5 volts DC. It can just support more demand without a brown-out.
It will save you having to do it in the future when you upgrade or add other components that require more power - the main offenders being graphics cards.

A minimum of 500W was what I had decided on, but I don't really want to fork out another £50-£60 (for a decent one) just yet. I don't mind doing so in 6 months to a years time when I get a new gfx card too. But I hadn't budgeted for a PSU at this time, and now I have a CPU in front of me that I'm not sure quite what to do with!

This is probably the one I'd go for (Antec 550W TP2):

http://www.ebuyer.com/customer/products/index.html?rb=24517065116&action=c2hvd19wcm9kdWN0X3Jldmlld3M=&product_uid=114931

I'm sure it'd do the job, but do I need to spend another £65, or should I just give my current PSU the benefit of the doubt?

Personally, I think this system will need a PSU of a minimum of 400W+. I certainly think 350W is cutting it fine. I've seen similar systems being sold with PSUs of 430W upwards.

450w is plenty if you get a quality one.

some of the 500's are actually only about 430 anyway. THere are some good reviews at http://www.silentpcreview.com/article699-page1.html

they are into quiet high quality components and do a good job of testing PSU's. The above link is a roundup of recommended PSU's but they have lengthy individual reviews too.

You will probably only need something bigger than 500 if your going for DUAL VGA cards, or multiple multicore CPU's.

My PSU died last week and I got an Antec True power trio 550, was $99.95 with a $50 instant rebate :) It doesn't have anything fancy like modular cables, only one large 120mm fan. But its quiet and seems to be pretty good quality.

Thanks guys. I'm pretty sure I'm gonna go for the 550W now rather than "trying it out". Although I might get away with a 430W, it's only a difference of about £10, and it should mean that I can definitely use it for a good few years yet.

Of course, I'm helping to justify that by selling a bunch of old gear (N64, 10 old ps1 & ps2 games, my old a1200 that's been sat in the loft for years)!

Not to turn on your computer, if that's what you're asking.

None.

That depends on how much you're under the mark.

The PSU is one place I wouldn't save money. If it where me, I'd get an overpowered one. Why? Because a 600 Watt PSU delivering 360 Watts is going to run a lot quieter and a lot cooler than a 400 Watt PSU doing the same.

If you had some generic 350, I would say no. But since it is an Antec, you should be OK with the stuff you are running.

I am also an advocate of good power supplies. I just bought a BFG 800W in case I want to add another 8800 to my system.