Analog to Digital Converter for my PC?

Hoping to get some help from the experts here on AG. 

I want to get the output from my TT into my PC (HP Envy beats audio) to do some sonic analysis of different record cleaning methods and products. I will most likely use Audacity or Reason as the software. My options for connecting an A2D converter to my PC are; USB or a single 3.5mm jack. 

1. What would you recommend for a decent analog to digital converter for around $500?
2. Is it worth the effort to upgrade my sound card to get L/R RCA jacks? 
3. If so, what would be a decent sound card to look at?

Thanks in advance,