Have you heard of eBay Adcommerce?
It's a fairly new advertising tool for eBay sellers. It would certainly be helpful for someone like you who is selling highly competitive items.
The best part is you can choose how much you want to spend on using the tool, and your text advertisements are free to display.
You can find out more about it here:Link hidden: Login to view
Trying other sites like Yahoo or Amazon is a great idea, and something I really encourage. Bonanzle and eCrater are other examples of alternative platforms you can sell on.
We reviewed eCrater just last week so check out this blog to find out more about it: Link hidden: Login to view