Marc Compton , Jan 17, 2012; 08:38 p.m.
I understand your questions and know that the Computer world is full of options and it can be confusing. You sound like you have a grasp of the important parts in a system, so I'll try to keep this short and simple. First saving a little money now, could cost you time and energy later. Buy the best you can afford, and always look for the best "bang for the buck" in every component. If an i7 Processor at 3.4ghz is too expensive, it is likely that an i7 at 2.8Ghz will suit just fine, and you would probably never even notice the difference.
Windows 7 64 bit is a fantastic OS, but you must keep in mind when you purchase other software, get the 64bit versions. Go with a Solid State drive if you can find a decent deal on one... the are fast and reliable and the prices have come way down in recent years. Again find the best value in terms of size, no less than 60gb though, in my opinion. Your second drive will be your storage drive, get at least a 1TB, but storage is so cheap getting a 2TB is not out of the question if it fits your budget. You may consider getting a RAID set up for backup purposes, however you have many options there to consider. Backup is it's own issue.
Graphic cards are tricky. There are some decent on-board graphics cards nowadays, but I would look into an actual card. nVidia makes a lot of good ones, I would get one with at least 1gb memory... lots of choices here, just do some research. I speak in dollars, but you should be able to find one around $100 that will suit your needs.
Sound card is not necessary, but are affordable. If it fits your budget, get an affordable one now when you have this built.
You have lots of choices in the Monitor department... LEDs are gaining popularity... Dell makes some great ones... look for the UltraSharp ones.
Final note about this... be sure whomever builds this supplies you with a proper Power Supply. Spend a bit extra here so it is not always running at 100%. If you over strain your PS it will fail quickly.
Hope this helps.