Can someone with some 1st hand experience please tell me whether it's worth the extra cash for one of these? Does it really tidy up the internals?

I have a psu with modular cables, and its a nice feature to have, but I could live without it. I would actually perfer a non-modular psu with the case I have now. The area where the psu rests in is really tight, and jamming my hand in there trying to hook up another cable isnt exactly fun.

Which power supplies are you looking at?

Well some people swear by them, but I am partial - many a customer I would hand off a clean build and give them a pack of the unused cables to store on their own initiative. Years later they contact me and they "lost" the unused cables and/or the hdd/dvd mounting brackets.

My bad, currently I zip-tie them to one of the unused 5.25 bays or secure them to the bottom of the case. Or if you do not have modular just route the unused cables out of the way and zip-tie them to the bundle toward the top of the case. Here is an old pic of my game rig...

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note all the power cables are in the background and only in the foreground as they migrate from the rear case fan onto the motherboard. The only interruptive airflow cables are the yellow IDE ribbons. The PSU is a PCP&C ATX510 non-modular and the unused ones are above the PSU itself.

Another example - my kid's PC
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Since there is no room above the PSU to organize I just zip-tied the wad of unused cables just outside the psu adjacent the DVD drive. The only interruptive airflow cables are the ribbon IDE and the PCIE power cables to the GPU. If the case had a top-mounted blowhole exhaust fan I probably would have chose one of the unused 5.25" bays to take up the excess cabling.

So in either case work needs to be done to get the cabling out of airflow as much as possible, regardless of a modular cable PSU.

I am looking at one of the Corsair supplies or a Seasonic M.

The main reason is that I find my case an Antec P180 to be a real pig with my current PSU - a Tagan 480W - in that most of the cables are stretched tight just to reach. The other reason is of course that I want a DX10 card and need more oomph!

To be honest I suppose what I really need is a PSU with longer cables.

Modular does not really add much in cost. And yes, it is helpful in tidying up a case and improving aesthetics and airflow.

It's not that big of a difference in cost really, but I prefer modular just for the neatness factor. A modern psu can have around a dozen seperate wires and many people don't even use half of them. It's nice to be able to disconnect what you don't need and keep things neat while still knowing if you do any upgrading you're still covered.

I just recently bought a silverstone strider 850w modular and I'm happy enough with it to recommend it. It's Fully modular, all sleeved cables has the 8-pin pci-e 2.0 connectors and comes with a nice little velcro pouch to keep all your unused cables in. It's also relatively quiet for a psu that size.

I agree with yellowbeard, less cables=more air flow= lower temps.
Plus corsair is made by seasonic.

I love em. I've had 2.