I will be in Osaka for two weeks starting today and was wondering if anyone can advice me on good stores to go to.
I know of Mint Record and of course the Hard Off and Book Off chains. Does anyone have any other tips for me? I can even go to Wakayama.

If you're there for 2 weeks I would see what you can buy and pickup locally on YJ.
May be worth the risk?

In Osaka, your best bet would probably be Den Den Town since it's like their version of Akihabara.