You can in general trust Ebay sellers I'm one after all but I personally wouldn't buy a PC from them because I would be worried about the warranty and the quality of the parts. Because of this I would be looking at one of the many computer manufacturers that have been about for some time such as Dell, Evesham, etc etc. If you go to one of the bigger companies you have the option, if you wish of going for a longer warranty. How much this costs varies, I don't bother with this mainly because I have built a few PCs and am used to replacing parts etc. But if you're not happy doing this its an option. I'm afraid I've never heard of this fancy sound card you have but as long as it works with XP there won't be an issue.