Some sound questions in general

Hey guys, I'm currently building a new comp and sound is one area I'm still undecided on. I'm currently using my Audigy 2 ZS and was considering keeping it for the new system, but should I consider upgrading to X-Fi? I was looking at the Extreme Music one. Also, I currently have the old Cambridge Soundworks 4.1 speakers originally meant to be used with Sound Blaster Live! years ago and I want to upgrade my speakers. I was looking between the Logitech Z5300, 5500, and the Klipsch Ultra ProMedia 5.1. Which should I go with? Is the Klipsch worth the extra 400 bucks? Lastly. one thing I liked about my current speakers is the rear ones have speaker stands, but I have yet to find any set of speakers with rear stands for sale. What should I do? nail them to the wall? And if I do that, would it be ok to nail them higher up like near the ceiling? Because otherwise I'd have 2 speakers in the middle the wall and that'd look odd. Anyways, any help would be appreciated! Thanks!

once your have an Audigy 1 or better you wont notice much difference between any of the models

You could buy a better graphics card instead. If you like the speaker system you have, get a couplle more satellite speakers and or sub woofer. the output levels can be adjusted to get the 7.1 system balanced. x-fi has a newer eax system. The spekers you have will work with it as well.