Best comp site I use when building my own computer....
http://www.anandtech.com/bench/CPU/39
They have benchmarks for all major brands of GPU and CPU.
Start by deciding on the CPU and GPU performance you are aiming for. You can do side by side comparisons across benchmarks...if you don't know what a benchmark does, you can either look it up and find out what it measures..but generally, I just use these for comparison across items. Once I have the name of the item I go shopping! My suggestions on shopping:
Buy your CPU first. Choose it based on comparative performance, then shop it to be sure you are willing to pay for it. Once you have the CPU, choose the video card in a price range you are comfortable with. I generally buy mine in the $270-300 US range. That is not bleeding edge, generally is 2 gens from top edge...again pay for what you can afford, the faster the better..but the more expensive. If you are using Oculus Rift, then go as high as possible...
As far as RAM...this is dependent upon who you want to believe...name brand or cheap...some claim name brand only for specifics related to timing, heat dissipation, etc. Honestly I've run it all and have never had a problem...since all RAM comes with limited lifetime warrantees...your choice, I would say 8 Gigs will do most with gaming no problem...particularly with 32 bit games...however, I you do any photo/video editing 16 Gigs is the way to go.
Ok brands I always use..because I found them most stable. Building computers for a living for 10 years also shapes my opinions...but again, these are mine. Your mileage may vary.
Mainboard: Asus. I love their new GUI BIOS, all models within a family have a huge set of base features..their base model in any family has many great features...and all family related boards are identical to the base, with more bells and whistles. Asus BIOS has some great features including (all can be handleed with their automated system or you can pick and choose your settings), multiple core load balancing, auto overclocking, memory overclocking, etc.
CPU: Intel. Sorry AMD I have no love for you. Intel just works. Always.
GPU: Nvidia. Personally like the EVGA company for their versions. Anytime I've had warrantee issues, RMA's issued quickly and can work with you for cross return rather than the regular one way then the other way return process. Can get you back on your feet faster.
Personally, I just pick whatever is on sale for HD's...most are fine...I would look at Solid State drive if you are playing games...Most will advise you to put your OS on an SSD for faster boots...I'm still leary of this, as SSD's failures are non recoverable. Regular HD's will sometimes give you warnings before they fail...SSD's do not. They work, then they do not. If you want to you can spend money on a HD that spins at 10,000 RPMS for faster reads and writes.
Sound. This is interesting as I've come to believe the exterior sound setups are much better than the internal cards and onboard sound. I suggest some research on computer sound cards, DACs, and Amplifiers. I watch videos with my external computer speakers, but play games with my headset and USB mixing board, increases immersion..but also sounds way better! My suggestions with your $3000 could be spent entirely on the sound setup very easily! ;P
Anyway, there's my suggestion on how to move along with your project! Good luck!