Hello, SPCR. I've been lurking for a while, so I'm glad to finally say hi. I am thinking of building a desktop for home use along the following lines, and would love any advice.

I want to run Ubuntu and Windows 7 simultaneously (with a VM). The Ubuntu side is for playing music (with MPD), backing up other computers in the house over rsync, and general internet and household use. The windows side is for playing DVDs, streaming Netflix, serving the printer, and anything else that is a hassle in Linux. (I like wrestling with Linux for my own education, but my wife has limited patience for things not just working all of the time.) I'm not a gamer, but it would be good to satisfy an occasional interest in a game without worrying too much about performance. I also do occasional image, video, or sound editing, but nothing too heavy.

I'm thinking of installing Ubuntu and running VirtualBox VMs of both Ubuntu and Windows 7. It may be excessive, but I really like the idea of having all of the setup effort to get the server working done in VMs so that I can swap out the hardware as needed, save snapshots, etc. Also, I just get a kick out of virtualization.
I'm not a dedicated computer guy, but I want to learn whatever is necessary to get it done right.

I want to spend around $800US or maybe a little more over time. I have an existing desktop (slow and noisy) that I am planning to replace piece by piece, starting with the motherboard and CPU and then extending into the rest in order of noisiness. The existing machine is an ATX tower with a 380W PSU and a few hard drives that I bought with noise in mind.

As long as I'm spending some money on this thing, I want it to feel zippy, even though my use may not require much. I'm also thinking that using RAID1 for a pair of backup drives would give me some peace of mind. Other than that, I'm not sure what I'm looking for.

I'm thinking of starting with an Intel Core i5 2500K CPU on a Gigabyte GA-Z68A-D3H-B3 motherboard, with maybe 16 GB of RAM. The next stop might be a quieter PSU and an SSD drive for the OSes. After that...a new case?

Am I crazy? Is the i5 overpowered for what I need? Will these components allow me to gradually move towards a quiet system? Is this whole double-virtualization idea nuts?

Thanks in advance for any advice or comments!

Maybe things have improved but high-res videos and games used to trouble with Virtualization. I guess you might be able to brute-force the video problem but there's no way you'll be able to play even a modestly demanding 3D game without your VM being able to use your 3D hardware.
I can't tell you how things have progressed. Maybe you can easily have OpenGL pass-through that works well now. But what if you have a Linux host and want to run a virtualized game which doesn't want to use OpenGL but some Microsoft way of accessing the GPU instead?
In general, I would prefer not to run VMs on top of Windows but if you could run your games outside the VMs, you'd probably spare yourself some grief. Now if you really want to virtualize your games, there's probably a way.
Maybe someone knowledgable about virtualizing GPUs will show up and maybe you should seek advice elsewhere.
Just know this: there's a feature the 2500K doesn't have which could potentially make your life easier. It's called VT-d and if it turns out that it's the only good way to do what you want reliably, know that other Intel chips such as the non-K 2500 have it.

Another word of warning: the 2500K should be obsoleted in two weeks (unless the release date has changed again). Z68 may already be obsolete (I don't know).

Other than that, yes: it sounds like a 2500K would be overpowered and so would Z68 which last I heard has some features which only work in non-virtualized Windows anyway. If you want to take advantage of overclocking while staying quiet, you'll need a serious cooling system. Nothing extraordinary mind you, but you'd need room in your case, to be willing to spend a little extra and so on. If you want to replace a non-ideal system piece by piece, perhaps you'd be better served by something easier to cool since the lesser Intels are plenty fast already. But if your case can handle a hot CPU, maybe you can justify spending a bit more for the fastest non-HT quad-core which has the features you want.
In any case, do give some details about your case and its ventilation if you want specific suggest CPUs, heatsinks and so on.

I would really hold off on buying the 2500K. Intel's Ivy line will be coming out (as was intimated above) in about a week and the prices are not bad at all. See:

http://vr-zone.com/articles/intel-cuts-desktop-ivy-bridge-cpu-pricing-ahead-of-launch/15557.html

But for your specific needs, you should really looks at the Xeon line of CPU's- especially

http://www.newegg.com/Product/Product.aspx?Item=N82E16819115083&SortField=0&SummaryType=0&PageSize=10&SelectedRating=-1&VideoOnlyMark=False&IsFeedbackTab=true#scrollFullInfo

This CPU is built for the VM environment, will run happily with regular (non-ECC) memory, and can be plopped into just about any Asus, Asrock, or Gigabyte socket 1155 motherboard available. This particular processor is without a graphics component which I see as a good thing. It runs very cool and very solid. Also unlike the 2500k it has Intel Virtualization Technology (which you want) as well as having Hyper-Threading Technology (like the i7 CPU's).

As to your other needs:

If you aren't in any rush you can wait for the Intel 330 SSD's to arrive:

http://www.fudzilla.com/home/item/26622-intel-slashes-the-cost-of-ssd

You may have noticed that the prices of many current SSD's have been dropping in anticipation of the launch.

Finally, if you need a very good Video card for a non-gamer, look to the Radeon HD 6450 products (fanless, of course). And always use Coolpacks to lay your hard drive on.

If you want to do this with any decent performance, you need VT-d, so that excludes using -k cpus, you're better off with a plain 2600. With VT-d you can do gpu passthrough.

Wow, I'm glad I asked. I might not be able to sort through all of your advice until the weekend, but I wanted to thank everyone who responded. Thanks!