What is best in my situation?

Hello,
windows 7 is just about to be released.

I find in Amazon [in UK] Windows Ultimate full version is £10.00 cheaper than the windows 7 ultimate upgrade version.

I 've got Dell's OEM Vista Ultimate 64 bit.

My computer is a

Dimension9200/DXP061

Intel Viiv Dual Core E6400 [2.13Ghz, 1066Mhz]

Memory Dual Channel 4GB  4 X 1GB [800MHz] DDR2

Graphic card: NVIDIA GeForce 7950 1GB Single

Sound Card: Sound Blaster X-Fi Xtreme music

DVD +/-RW[read/write] 16x max and DVD [Reader] 16x [2 drives]

Dell Wireless Bluetooth Keyboard & Mouse Wireless Bluetooth

Genuine Windows VISTA Ultimate 64 Bit with Service Pack1

What is tthe best option for me to buy the full or the upgrade version of the Windows 7 64 bit?

If I install the full windows 7 64 bit on my computer, will I loose the Dell's OEM rights for my VISTA Ultimate 64 bit?

When installing the Windows 7 64bit OS, Do I have to first down load all the necessary drivers such as chipset,video,sound ect on a disc prior to I commence my installation of the windows 7? -If that is the case is it easy to get the correct drivers for my computer from intel,Nvidia,Creative sound since my computer is over 2 1/2years old!!

I value your opinion so greatly as with your help only I was able to do a clean install of my present vista ultimate 64bit os in my computer before.