Buying a GTX 260, want to make sure everything will work

Well, after a load of googling, I'm finally just going to ask.

I'm about to buy a GTX 260 core 216, and am thinking of adding another later, but want to make sure I'll be able to do that. I have a 750w psu, but it only has 2 6-pin connectors, and 2 8-pin connectors. Seeing as the 260 needs 2 6-pin connectors, can I get 8-pin to 6-pin adapters later on if I want to add another 260? Here's a link to my PSU: http://www.newegg.com/Product/Prod [...] 6817171024


Here's my specs just in case

4GB of DDR2 ram (upgrading to 8GB when I get 64-bit)
XFX 750i SLI motherbored
Intel 2.5GHz quad core processor
1TB HDD
DVD drive
ect.

Also, I'm upgrading from a 9800GT, is there anything I could do with that besides boxing it back up?
EDIT: Would it be worth it to use it as a dedicated PhysX card?

One last thing, what would you say I do about cooling after I get this. Currently my case has a 120mm fan on the front, 2 80mm fans on the back, and an 80mm on the side. There's room on the motherbored side of the side for another 80mm fan, should I get one?

Answers to any or all of the questions would be great.

Thanks.