ATI Graphics Question

This is probably a really obvious question, but it's been a while since I've looked into video cards..

I built a computer two years ago, and I originally installed an x 1950xt. I have an asus p5w mb, and it has 2 pci x16 slots so I was planning on eventually using crossfire.

Anyway, you can't find the CF edition of 1950xt on the web (yes, the one with the external 'dongle') and last time I looked they were about 200$ more than an 8800 GT, which would make it a bad choice to buy anyway.

So, I've decided to scrap the x1950 xt and buy an HD 4000 series card, and I have a few questions.

If you have PCI x16 1.0 slots and you buy a 2.0 card, will you see that much of a difference taking it back to 1.0 or do the 2.0 cards currently on the market not really take full advantage of the 2.0 bandwidth to start off with? Another way to re-word this is, would it be a waste to buy a 2.0 card and use it in a 1.0 slot?

I also remember something about if you have 2 cards in crossfire you will NOT be able to have a dual screen configuration unless you install a third independent graphics card to support the second monitor. I'm not sure if this still holds true because CF cards are now internally bridged or connected by the driver.

Finally, I can't figure out which of these two cards will perform better (At 1680 x 1050. The first would probably outperform at higher resolutions, but then again I'm not really sure because of the slower memory clock..) They are both about the same price as well. (~225$)

I'm also open to suggestions for other cards.


Card 1:

SAPPHIRE 100259-1GL Radeon HD 4870 1GB
mem clock: 900 mhz 3.6 gbps

Card 2:
HIS Hightech H487F512P Radeon HD 4870 512MB
mem clock: 1800 mhz


Thanks in advance for any help