Speed?
You need a quad core. Multi-threaded applications be damned. If you're doing anything heavy, you'll probably be multi-tasking, so you can multi-thread the good old fashioned way. Having a quad core practically negates any sort of performance hit from a virus scanner in the background while gaming (not ideal example, but everyone has experienced this on a single or dual core). I recommend either a phenom II 955 or i5 750. You can always disable cores or run a program under 1 core with imagecfg.
If you really want fast, you'll learn CUDA or stream and start using your GPU to do the work for you. $700 is awkward for GPUs, since the 460 is too expensive, and the 5770 is too cheap. Get the 5770.
Grab any old seasonic PSU, though for SPEED this doesn't matter (it's quality). You can use
this custom google search to search through all the reputable PSU reviewers. I prefer hardwaresecrets, but there's a buttload of PSUs out there. What you're looking for in PSUs is efficiency, safety protection (usually a max power which is over the rated power, but then shuts off to prevent circuit damage), general quality of components (japanese capacitors, usually chemicon), ripple on the 12 V rail (20 mV is god tier, 40 mV is awesome, 60 mV is meh, 80 mV is poor, 120 mV is exploding), and the reviewer's rating of the PSU. Seasonic is the undisputed best in PSU manufacturing, and they sell to corsair, antec, PC Power & Cooling, and others, though those also buy from other companies like CWT. Don't overpower your PSU either, since it's less efficient. The only people who need an 800W power supply are those running dual GPUs or a really heavy fermi system.
Case doesn't matter for speed. See previous recommendation thread for 2 decent cheap cases. Lian Li is best in quality, but there's tons out there, like Cooler Master, and a few others who make excellent cases. You'll usually get what you pay for unless it's Antec.
CPU cooler (you want speed, so you're overclocking, right?) I'd get the scythe mugen, that big hunking noctua DH 14 or whatever, spire thermax eclipse II, or tuniq 120 extreme. There's another one which is really dirt cheap but really really good too, but I forget what the name was, sorry.
For ram, the actual specs don't matter TOO much. Obviously you want faster ram, but there have been tests with low cas RAM and low speeds vs high cas RAM and high speeds, and they performed equally well, meaning it doesn't matter too much. Make sure you get something affordable and with heat spreaders. I've about given up on recommending any sort of DDR3. 4 GB will be plenty, but 8 GB is even better if you can get it. Remember you can always upgrade it. Music can get pretty heavy, as can image editing, but I have yet to come close to using my 3.5 GB.
Optical drive doesn't matter, get a cheap $20 one, try to find a combo deal, since you can get them for free/50% off that way.
HDD is caviar black or spinpoint f3. If you want speed, it's the spinpoint. If you really want speed, check out
passmark for SSD listings. ewiz typically has really good deals on hard drives, better than newegg.
Motherboards I recommend are Asus, Gigabyte, MSI, and DFI. Apparently ASRock=Asus, and Biostar has impressed me with their website and support. Foxconn is sort of notorious for burning up CPUs, and ECS is just poor quality. EVGA makes superbly expensive motherboards, but good just the same.
This i5/evga combo isn't too bad with the MIR, but you still have to justify spending $60-$40 more on an EVGA board over a cheaper biostar/asus.
If you're working with sound, you'll probably want a sound card, but I'm not an audiophile, and unless you have the speakers to utilize the sound quality, they're mostly worthless.
If you want me or ex to make you a build on newegg, we can.
"Parliamentary inquiry, Mr. Chairman - do we have to call the Gentleman a gentleman if he's not one?"