Well if your sure the audio out is on multi out only, not hdmi and multi, then you should have no echo or delay. I run video through hdmi and audio through multi out and dont get your issues.
Even though it is a new laser, Id still recommend a gentle cleaning with a q-tip and rubbing alcohol. I was having same issues after a deck replacement on my slim, and this worked for me.
Well here comes the questions.
What are you looking in a full tower case?
What components are you trying to fit in said case??
Are you partial to coolermaster, or can we give other suggestions?
ETC ETC, basically we need more info!!