I'm building my first computer. I want to build for the future at a reasonable price. I was thinking of the Corsair TX650, but the OCZ modz600 looks attractively priced.Is there much quality difference?
Thanks
Personally I wouldn't buy anything OCZ, but hey...
Corsair, Cooler Master, Antec, Seasonic and a few others make decent PSUs, but it's important to look at what you're getting depending on what you want out of a PSU.
I'd say get something that's 1. 80+ certified, as it'll save you some money on the electricity bill, as those PSU's are more efficient in terms of power usage 2. a multi-rail PSU (i.e. it has multiple +12V rails) as it's safer if nothing else (especially as you start to exceed 500-600W) and generally works better except potentially for professional overclockers and 3. something that's quiet, as you don't want a really loud PSU.
A modular PSU is generally easier to build with and a lot tidier, but it's pointless getting one with a removable ATX cable for example, as you have to use that cable no matter what.
You don't appear to have very powerful hardware, although you haven't listed your graphics card, so it's a bit hard to say, but even a 500-550W PSU should be more than plenty for your needs. Idling at the desktop, a mother PC doesn't use more than about 100W and unless you've got a very powerful graphics card it's unlikely that you'll ever exceed 300-350W.
Personally, I'd get something like this
http://www.newegg.com/Product/Product.aspx?Item=N82E16817151093 or if you're on a budget, this
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139028
