used Hd cards: pcix or express?

[starburst]

Guys, bit confused.

I want to pick up a used HD system.

Pci-x cards are much cheaper than the new express version on ebay. Would you say its better to invest in the express version? Are the x version compatible with pt 10?
What year did the mac pro move to pci express?

Now thinking about the mac pro. My understanding is a 2010 spring model would give me access to the current os and pt 10, but what about pt 8 and 9? Pt 10 is still too costly for me but I imagine when pt 11 comes out prices will drop dramatically so pt 8 or 9 would do me for a year or two then I can pick up 10 later.
Hoping for some advice. Thanks.