Q1.. So is it possible to have only 8Gb in two sticks – then add two more 4GB sticks later?
Yes you can run only two sticks and later add 2 more sticks. It would be best to end up with all four sticks being the same brand and part number. Doing so is hit or miss because you may or may not be able to find the exact same memory later when you decide to add eight more gigs. You may need to drop the speed from 1333 to 1066 or loosen timings etc. to get 4 modules stable.
Q2. For my MoBo and CPU could you give me an exact memory stick that would work in my situation?
Gigabyte tests very few memory brands and types so their QVL list for ram is not very useful. I normally use Corsair or Crucial memory in all my builds. Both have a memory configurator on their site. Corsair here
http://www.corsair.com/configurator/product_results.aspx?id=1536858#other_modulesCrucial here
http://www.crucial.com/store/listparts.aspx?model=GA-890XA-UD3Since you are not going to over clock normal 1333 memory should be fine. Write down the part numbers for all the 1333 8 gig kits from both manufactures and then see which ones you can find for purchase from the supplier you want to use.
Q3.. I understand that one could use as much power as one can get. I understand 700+ watts is good. How do you know what is a good quality pwr supply? Could you recommend a power supply that is reasonably good quality and over 700 Watts?
Power supplies are the most important part of a PC build. I use Corsair or Seasonic supplies when possible. Most Corsair supplies are made by Seasonic. Looking at your build I would think a quality 550 watt supply would be all you would need. To be sure enter in all your hardware here and see what you need for sure.
http://www.extreme.outervision.com/psucalculator.jspQ4.. If I run Windows 7 Ultimate 64bit can I typically run 32bit software on a 64bit operating system (assuming that the software in question would normally run under Windows 7 32bit)?
32 bit OS's only supports 4 gigs of ram so you will need to install 64 bit windows 7. Most if not all 32 bit programs work fine in Windows 7 64 bit. Note any 32 bit programs used will not be able to use more than 2 gigs of memory. This is not a limitation of Windows 7 is a limitation caused by 32 bit programs. To use the full potential or your new PC you may need newer versions of the software you use. AKA photoshop, video editing software etc. Do some research on the versions of the programs you are going to use. Do they support Windows 7? 64 bit etc.
Q5.. What would you recommend as a DVD/CD reader/writer (I have been writing –R format on DVD and CD in the past)?
If you burn lots of dual layer DVD's a Sony Optiarc drive that uses a NEC chipset would be a good choice or any drive that uses a NEC chipset. If you do not burn many dual layer DVD's Lite-On drives that use the Mediatek chipset are a good choice. You may want to get two drives, one using the NEC chipset and one using the Mediatek chipset and have the best of both worlds. Asus makes a Lite-On clone that uses the Mediatek chipset and they are very reasonably priced. I just love all 5 of mine. New egg has them in stock.
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007589+50001315&QksAutoSuggestion=&ShowDeactivatedMark=False&Configurator=&IsNodeId=1&Subcategory=5&description=&Ntk=&CFG=&SpeTabStoreType=&srchInDesc=I have DRW-24B3LT's and DRW-24B1ST's. Keep in mind not all Sony Optiarc drives use the NEC chipset and not all Lite-On drives use the Mediatek chipset. Most Sony Optiarc drives are actually made by Lite-On and may or may not use the NEC chipset.
edit, updated burner info
Bill