I would recommend that you consider a i5-750 processor ($200 USD) and a P55 motherboard (Gigabyte P55-UD4P or ASUS P7P55D PRO: $170 USD). Both of these motherboards will allow you to add a second graphics card in the future. This system will actually outperform a i920 processor because the i750 processor has the latest technology advancements from Intel: http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=364...
I would combine this with a Hyper 212 HSF ($30), 4GB of DDR3 1333 ($95), a 5770 GPU ($175), a WD Caviar Black 1TB HDD ($100), any CD/DVD Drive ($40), Antec 900 Case ($100), and Antec EA750 PSU ($100),). This totals $1010 USD which should be close to within your budget of $1200 CDN. You may be able to find combo deals, rebates, or other sales to get the cost down.
The case is a personal choice. I just added the Antec 900 case in the mix because it has lots of room and has excellent cooling. Another good case to consider is the HAF 922.
This initial build would also allow you to add a second graphics card in the future if you wanted without having to upgrade either your motherboard or power supply.
I would not recommend that you setup a RAID array. The performance increases are small, and consumer grade drives can cause problems with error correction routines used in RAID controllers. HDD made for RAID (Enterprise Drives) are very expensive.
The above system would perform extremely well for your applications, and allow easy upgrades (additional graphics card or hard drive) in the future.
Click pricematch at the bottom of your cart, copy & paste the URLs & prices in the appropriate boxes. nicx does pricematching. The only rules are the item must be in Canada & in stock. newegg.ca doesn't, but their selection is pretty good. Also, their total includes brokerage fee & 13% taxes vs 5% tax for NCIX if you're from out of the province.
If you think you might want to add a second graphics card at some point in the future, you should get one of the motherboards I mentioned because they support SLI or Crossfire. Along the same lines, you should get a minimum 650 W power supply to support two GPU cards. Corsair and Antec make great power supplies. I do not know anything about OCZ power supplies, so I will defer to others.
If you decide you will never have two graphics cards, then you can get by with a cheaper motherboard. There are many very good P55 motherboards in this category for about $120 to $140 USD. I apologize for not knowing the Canadian prices, or the Canadian websites.