Re: Build or 'out of the box'/'off the shelf'?

Yes and no.

If you are editing full HD, you are going to need a beefy machine wih lots of RAID drive space. If you are editing DV, not so much so. But, it also comes down to what you plan on doing, eg. layers, effects, and such. Even with DV, the more you add to your timeline, as far as layers, text, and effects, the longer your renders will be. A few layers in a :30 project and you could be looking at an all-night render, even with DV, if your hardware isn't up to it.

The software out now will handle whatever you want to edit. I do suggest, so you don't have to re-learn software, to pick up something that can handle your low-end home videos, then you can move to the higher end stuff while remaining with the same software. Final Cut Pro and Adobe Premiere Pro are both great for this. I like Final Cut Pro on the Mac a little better, but Adobe Production Premium is well integrated and well worth the money. Then, if you like, you can get a system that will handle your home DV well enough (single dual core processor, single video drive), learn the software, then move up to a beefier machine to handle your higher end stuff (dual quad core processors, 4 or 5 drive RAID array).