I have a Linksys WMP54GS however i can get this card to work under slackware13 i would like to get WMP600N which is a newer card and i've heard that it works just out of the box with linux... so i wonder if any one has a different opinion on this... thank you.

maybe i should go CAT6a...

Cat6 all the way. I will never go beyond G for wireless and it's only used for web browsing. I hated crawling through my attic running cat6 cables, but it's well worth it. Now, I don't get a single pause running multiple HD streams.

ok, Cat 6A STP (Shielded Twisted Pair), Solid Conductor...

now, where should i buy?

Shielded is not necessary unless you will be running tons of cables together or expecting a lot of interference from other sources. Unshielded should do just fine for home use. Plus you will save a lot with unshielded. I use both and do not notice any difference. I also kept my network cables away from the power lines.

Check major online vendors (ebay, amazon, newegg, etc) and compare prices locally. I find local shops in my area had better deals, when you factor in shipping cost, for orders less than 1000ft. Also, get enough cable so you can do multiple pulls at the same time. If you think you will need a little over a 1000ft, get two 1000ft reels. This will save a lot of time + you will find use for the extra cables.

thanks for the advice.