most 8-9spd stuff is compatible, I always thought... don't quote me on that, but still... stay 8 speed if you choose. You'd need new shifters at the very minimum to upgrade to 9spd. The newer SRAM stuff is wonderful. I've toyed with the X-9 stuff and it shifts like absolute butter. The crankset I linked you to is an absolute steal for sure. Plus it's ISIS splined so you'll have a rather large choice in BB's & cranks. Shimano uses Octalink and while most BB's are available in that format, you'll probably find more ISIS stuff. Plus it's being championed by various companies (Chris King was in on the original design if I remember correctly) as more of an "open" standard than Octalink. Reminds me of the Windows/Linux debate. As far as the chain goes, stick with SRAM or wipperman. Both use a "powerlink" of sorts that allows quick and painless chain removal in a pinch. Some people like the wipperman chains better, others prefer the SRAM. Generally everyone seems to prefer the SRAMs or wippermans over the Shimanos.
Here's the 8-spd sram cassette... only $22, good deal if you ask me..
http://www.jensonusa.com/store/product.aspx?i=CS708B16
and here's the chain to go with it
http://www.jensonusa.com/store/product.aspx?i=CH707A01