New Vga card

Hi, i am thinking to get a new vga card.

I am thinking about these:
GTX 280 1Gb
HD 4870 X2

I like playing games with full max out and of course the new ones!
I do play now at 1280x1024 but soon i will get a 22" TFT monitor which supports 1680x1050. I am very pleased with the X1900XTX which last 2 years and i would like the new card to be able to last that long too.

Also, i would like to ask if my PSU will be enough for these cards, it has only 2x6pin connectors, will i be able to run the GTX 280/HD4870x2 which needs 1x6 and 1x8? Where i can get a 6 to 8 pin???Or should i get a new one?
And one last thing, i sure my cpu will bottleneck the cards, should i get a new one? and if yes which one.

I am also thinking to get a HD4870 for now and when the new cards are out to upgrade my pc with getting new cpu(Bloomfield)/psu/vga/motherboard

These are my current specifications

OS: Win Vista Bus (64-bit) / Win XP (32-bit)
CASE: Thermaltake VA9000BWS Kandalf (Fans: 2x120mm & 2x90mm)
CPU: Core 2 Duo E6600 (2.4Ghz)
CPU COOLER: Zalman FS-C77 Fatality
VGA: Gigabyte X1900XTX 512MB
MTB: ASUS P5W DH DELUXE
HDD: Western Digital 320GB SATA II & Western Digital 150GB @ 10.000rpm
RAM: 2x1GB & 2x2GB Corsair PC6400 (800Mhz)
PSU: Tagan 580 W
MON: LG 19'' LCS L1919S-SF (1280x1024)

Thanks in advance!

What about the power supply? 6 to 8 pin connector? Is this a good idea, using 6 to 8 pin connector?